diff --git a/lib/xos-genx/xos-genx-tests/helpers.py b/lib/xos-genx/xos-genx-tests/helpers.py
index 4687bb3..e6d87ab 100644
--- a/lib/xos-genx/xos-genx-tests/helpers.py
+++ b/lib/xos-genx/xos-genx-tests/helpers.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import os
 
 # Constants
diff --git a/lib/xos-genx/xos-genx-tests/test_cli.py b/lib/xos-genx/xos-genx-tests/test_cli.py
index 3f94865..087c904 100644
--- a/lib/xos-genx/xos-genx-tests/test_cli.py
+++ b/lib/xos-genx/xos-genx-tests/test_cli.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 import os
 from mock import patch
diff --git a/lib/xos-genx/xos-genx-tests/test_django_generator.py b/lib/xos-genx/xos-genx-tests/test_django_generator.py
index a81f80c..022a640 100644
--- a/lib/xos-genx/xos-genx-tests/test_django_generator.py
+++ b/lib/xos-genx/xos-genx-tests/test_django_generator.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 import os
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
@@ -32,9 +33,9 @@
         args = XOSProcessorArgs(files=[VROUTER_XPROTO], target="django.xtarget")
         output = XOSProcessor.process(args)
 
-        fields = filter(lambda s: "Field(" in s, output.splitlines())
+        fields = [s for s in output.splitlines() if "Field(" in s]
         self.assertEqual(len(fields), 2)
-        links = filter(lambda s: "Key(" in s, output.splitlines())
+        links = [s for s in output.splitlines() if "Key(" in s]
         self.assertEqual(len(links), 2)
 
     def test_optional_relations(self):
@@ -59,11 +60,11 @@
         args = XOSProcessorArgs(inputs=xproto, target="django.xtarget")
         output = XOSProcessor.process(args)
 
-        null_true = filter(lambda s: "null = True" in s, output.splitlines())
-        null_false = filter(lambda s: "null = False" in s, output.splitlines())
+        null_true = [s for s in output.splitlines() if "null = True" in s]
+        null_false = [s for s in output.splitlines() if "null = False" in s]
 
-        blank_true = filter(lambda s: "blank = True" in s, output.splitlines())
-        blank_false = filter(lambda s: "blank = False" in s, output.splitlines())
+        blank_true = [s for s in output.splitlines() if "blank = True" in s]
+        blank_false = [s for s in output.splitlines() if "blank = False" in s]
 
         self.assertEqual(len(null_true), 1)
         self.assertEqual(len(null_false), 1)
diff --git a/lib/xos-genx/xos-genx-tests/test_field_graph.py b/lib/xos-genx/xos-genx-tests/test_field_graph.py
index cfb4c8b..c3c08a7 100644
--- a/lib/xos-genx/xos-genx-tests/test_field_graph.py
+++ b/lib/xos-genx/xos-genx-tests/test_field_graph.py
@@ -13,10 +13,11 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.jinja2_extensions import FieldNotFound
-from helpers import XProtoTestHelpers
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
+from helpers import XProtoTestHelpers
 from functools import reduce
 
 
@@ -75,7 +76,7 @@
             generate()
 
         self.assertEqual(
-            e.exception.message,
+            str(e.exception),
             'Field "B" not found in model "Foo", referenced from field "A" by option "unique_with"',
         )
 
diff --git a/lib/xos-genx/xos-genx-tests/test_general_security.py b/lib/xos-genx/xos-genx-tests/test_general_security.py
index c675b16..26a4736 100644
--- a/lib/xos-genx/xos-genx-tests/test_general_security.py
+++ b/lib/xos-genx/xos-genx-tests/test_general_security.py
@@ -12,28 +12,32 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
+from __future__ import print_function
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers, FakeObject
 
-"""The function below is for eliminating warnings arising due to the missing output_security_check,
-which is generated and loaded dynamically.
-"""
-
 
 def output_security_check(x, y):
+    """
+    This function eliminates warnings arising due to the missing
+    output_security_check, which is generated and loaded dynamically. This is
+    defined in the global namespace, and in python3 the globals() namespace has
+    to be passed to calls to "exec()" for the xproto-generated version to
+    redefine this function.
+    """
+
     raise Exception("Security enforcer not generated. Test failed.")
     return False
 
 
-"""
-The tests below use the Python code target to generate
-Python security policies, set up an appropriate environment and execute the Python.
-"""
-
-
 class XProtoSecurityTest(unittest.TestCase):
+    """
+    Use the Python code target to generate Python security policies, set up an
+    appropriate environment and execute the Python.
+    """
+
     def setUp(self):
         self.target = XProtoTestHelpers.write_tmp_target(
             """
@@ -48,10 +52,8 @@
     policy output < True >
 """
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-
-        exec(output)  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def output_security_check(obj, ctx):
@@ -68,10 +70,8 @@
 """
 
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-
-        exec(output)  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def output_security_check(obj, ctx):
@@ -93,12 +93,8 @@
 """
 
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-
-        exec(
-            output, globals()
-        )  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def sub_policy_security_check(obj, ctx):
@@ -130,12 +126,8 @@
 """
 
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-
-        exec(
-            output, globals()
-        )  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def sub_policy_security_check(obj, ctx):
@@ -165,9 +157,8 @@
 """
 
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-        exec(output)  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def output_security_check(obj, ctx):
@@ -192,9 +183,8 @@
     policy output < exists Privilege: Privilege.object_id = obj.id >
 """
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
-        exec(output)  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def output_security_check(obj, ctx):
@@ -210,7 +200,7 @@
 """
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
         output = XOSProcessor.process(args)
-        exec(output)  # This loads the generated function, which should look like this:
+        exec(output, globals())  # This loads the generated function, which should look like this:
 
         """
         def output_security_check(obj, ctx):
@@ -228,15 +218,15 @@
 """
 
         args = XOSProcessorArgs(inputs=xproto, target=self.target)
-
         output = XOSProcessor.process(args)
+        exec(output, globals())
+
         """
         def output_security_check(obj, ctx):
             i2 = Credential.objects.filter((~ Q(obj_id=obj_id)))[0]
             i1 = (not i2)
             return i1
         """
-        exec(output)
 
 
 if __name__ == "__main__":
diff --git a/lib/xos-genx/xos-genx-tests/test_general_validation.py b/lib/xos-genx/xos-genx-tests/test_general_validation.py
index 0e2a785..a2b5924 100644
--- a/lib/xos-genx/xos-genx-tests/test_general_validation.py
+++ b/lib/xos-genx/xos-genx-tests/test_general_validation.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers, FakeObject
diff --git a/lib/xos-genx/xos-genx-tests/test_generator.py b/lib/xos-genx/xos-genx-tests/test_generator.py
index 1de6bd8..8212d51 100644
--- a/lib/xos-genx/xos-genx-tests/test_generator.py
+++ b/lib/xos-genx/xos-genx-tests/test_generator.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 import os
 from helpers import OUTPUT_DIR
diff --git a/lib/xos-genx/xos-genx-tests/test_graph.py b/lib/xos-genx/xos-genx-tests/test_graph.py
index c6cfea7..1e73955 100644
--- a/lib/xos-genx/xos-genx-tests/test_graph.py
+++ b/lib/xos-genx/xos-genx-tests/test_graph.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
diff --git a/lib/xos-genx/xos-genx-tests/test_jinja2_base.py b/lib/xos-genx/xos-genx-tests/test_jinja2_base.py
index 859d640..3b988e5 100644
--- a/lib/xos-genx/xos-genx-tests/test_jinja2_base.py
+++ b/lib/xos-genx/xos-genx-tests/test_jinja2_base.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.jinja2_extensions.base import *
 
diff --git a/lib/xos-genx/xos-genx-tests/test_jinja2_django.py b/lib/xos-genx/xos-genx-tests/test_jinja2_django.py
index d5da2d3..9b993df 100644
--- a/lib/xos-genx/xos-genx-tests/test_jinja2_django.py
+++ b/lib/xos-genx/xos-genx-tests/test_jinja2_django.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.jinja2_extensions.django import *
 
diff --git a/lib/xos-genx/xos-genx-tests/test_optimize.py b/lib/xos-genx/xos-genx-tests/test_optimize.py
index c86b736..5791542 100644
--- a/lib/xos-genx/xos-genx-tests/test_optimize.py
+++ b/lib/xos-genx/xos-genx-tests/test_optimize.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.jinja2_extensions.fol2 import FOL2Python
 
diff --git a/lib/xos-genx/xos-genx-tests/test_package.py b/lib/xos-genx/xos-genx-tests/test_package.py
index 03911bd..d364431 100644
--- a/lib/xos-genx/xos-genx-tests/test_package.py
+++ b/lib/xos-genx/xos-genx-tests/test_package.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 import os
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
diff --git a/lib/xos-genx/xos-genx-tests/test_parse.py b/lib/xos-genx/xos-genx-tests/test_parse.py
index 8d1ccf5..ade625a 100644
--- a/lib/xos-genx/xos-genx-tests/test_parse.py
+++ b/lib/xos-genx/xos-genx-tests/test_parse.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
diff --git a/lib/xos-genx/xos-genx-tests/test_policy.py b/lib/xos-genx/xos-genx-tests/test_policy.py
index e8b5a76..9cac78a 100644
--- a/lib/xos-genx/xos-genx-tests/test_policy.py
+++ b/lib/xos-genx/xos-genx-tests/test_policy.py
@@ -13,10 +13,10 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import FakeObject, XProtoTestHelpers
-import pdb
 
 """
 The tests below convert the policy logic expression
diff --git a/lib/xos-genx/xos-genx-tests/test_pure_proto.py b/lib/xos-genx/xos-genx-tests/test_pure_proto.py
index c4f680d..fdf1fe7 100644
--- a/lib/xos-genx/xos-genx-tests/test_pure_proto.py
+++ b/lib/xos-genx/xos-genx-tests/test_pure_proto.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
diff --git a/lib/xos-genx/xos-genx-tests/test_rlinks.py b/lib/xos-genx/xos-genx-tests/test_rlinks.py
index c0ad406..67e31dd 100644
--- a/lib/xos-genx/xos-genx-tests/test_rlinks.py
+++ b/lib/xos-genx/xos-genx-tests/test_rlinks.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
diff --git a/lib/xos-genx/xos-genx-tests/test_swagger.py b/lib/xos-genx/xos-genx-tests/test_swagger.py
index 3af997e..1886a76 100644
--- a/lib/xos-genx/xos-genx-tests/test_swagger.py
+++ b/lib/xos-genx/xos-genx-tests/test_swagger.py
@@ -12,10 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
-
-import yaml
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import OUTPUT_DIR
 
diff --git a/lib/xos-genx/xos-genx-tests/test_target.py b/lib/xos-genx/xos-genx-tests/test_target.py
index c468018..4e70de7 100644
--- a/lib/xos-genx/xos-genx-tests/test_target.py
+++ b/lib/xos-genx/xos-genx-tests/test_target.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
 import os
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
diff --git a/lib/xos-genx/xos-genx-tests/test_tosca.py b/lib/xos-genx/xos-genx-tests/test_tosca.py
index c5a0f17..6e585f5 100644
--- a/lib/xos-genx/xos-genx-tests/test_tosca.py
+++ b/lib/xos-genx/xos-genx-tests/test_tosca.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
@@ -145,7 +146,7 @@
         args.inputs = xproto
         args.target = self.target_tosca_keys
         output = XOSProcessor.process(args)
-        self.assertIn("['name', ['key_4', 'key_3'], ['key_1', 'key_2']]", output)
+        self.assertIn("['name', ['key_1', 'key_2'], ['key_3', 'key_4']]", output)
 
         xproto = """
             option app_label = "test";
@@ -163,4 +164,4 @@
 
         args.inputs = xproto
         output = XOSProcessor.process(args)
-        self.assertIn("['name', ['key_1_id', 'key_3_id', 'key_2_id']]", output)
+        self.assertIn("['name', ['key_1_id', 'key_2_id', 'key_3_id']]", output)
diff --git a/lib/xos-genx/xos-genx-tests/test_translator.py b/lib/xos-genx/xos-genx-tests/test_translator.py
index 320021b..f98894b 100644
--- a/lib/xos-genx/xos-genx-tests/test_translator.py
+++ b/lib/xos-genx/xos-genx-tests/test_translator.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 
+from __future__ import absolute_import
 import unittest
 import os
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
@@ -335,7 +336,7 @@
         args.target = "modeldefs.xtarget"
         output = XOSProcessor.process(args)
 
-        read_only = filter(lambda s: "read_only: True" in s, output.splitlines())
+        read_only = [s for s in output.splitlines() if "read_only: True" in s]
         self.assertEqual(len(read_only), 3)  # readonly is 1 for ParentFoo and 2 for Foo
 
 
diff --git a/lib/xos-genx/xos-genx-tests/test_xos_security.py b/lib/xos-genx/xos-genx-tests/test_xos_security.py
index 3bd4653..b75f3c7 100644
--- a/lib/xos-genx/xos-genx-tests/test_xos_security.py
+++ b/lib/xos-genx/xos-genx-tests/test_xos_security.py
@@ -12,29 +12,29 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import XProtoTestHelpers
 
-"""The function below is for eliminating warnings arising due to the missing policy_output_enforcer,
-which is generated and loaded dynamically.
-"""
-
 
 def policy_output_enforcer(x, y):
+    """
+    eliminating warnings arising due to the missing policy_output_enforcer,
+    which is generated and loaded dynamically.
+    """
     raise Exception("Security enforcer not generated. Test failed.")
     return False
 
 
-"""
-The tests below use the Python code target to generate
-Python security policies, set up an appropriate environment and execute the Python.
-The security policies here deliberately made complex in order to stress the processor.
-"""
-
 
 class XProtoXOSSecurityTest(unittest.TestCase):
+    """
+    Use the Python code target to generate Python security policies, set up an
+    appropriate environment and execute the Python.  The security policies here
+    deliberately made complex in order to stress the processor.
+    """
+
     def setUp(self):
         self.target = XProtoTestHelpers.write_tmp_target(
             "{{ xproto_fol_to_python_test('output',proto.policies.test_policy, None, '0') }}"
diff --git a/lib/xos-genx/xos-genx-tests/test_xos_validation.py b/lib/xos-genx/xos-genx-tests/test_xos_validation.py
index 257eb4d..65555a3 100644
--- a/lib/xos-genx/xos-genx-tests/test_xos_validation.py
+++ b/lib/xos-genx/xos-genx-tests/test_xos_validation.py
@@ -12,28 +12,26 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from __future__ import absolute_import
 import unittest
 from xosgenx.generator import XOSProcessor, XOSProcessorArgs
 from helpers import FakeObject, XProtoTestHelpers
 
-"""The function below is for eliminating warnings arising due to the missing policy_output_validator,
-which is generated and loaded dynamically.
-"""
-
 
 def policy_output_validator(x, y):
+    """
+    For eliminating warnings arising due to the missing
+    policy_output_validator, which is generated and loaded dynamically.
+    """
     raise Exception("Validator not generated. Test failed.")
     return False
 
-
-"""
-The tests below use the Python code target to generate
-Python validation policies, set up an appropriate environment and execute the Python.
-"""
-
-
 class XProtoXOSModelValidationTest(unittest.TestCase):
+    """
+    Use the Python code target to generate Python validation policies, set up an
+    appropriate environment and execute the Python.
+    """
+
     def setUp(self):
         self.target = XProtoTestHelpers.write_tmp_target(
             "{{ xproto_fol_to_python_validator('output', proto.policies.test_policy, None, 'Necessary Failure') }}"