Add more explicit console logging + minor fixes

* The checks with keywords such as "Should Not Be Empty", "Should
  Be Equal As"... should have a more explicit message on fail, so that
  the console output shows a clearer failing reason.
* Other minor fixes included in the commit are:
	* The Sadis file comparison to None string.
	* The KUBECTL_CONFIG variable not properly set, altough
	  apparently unused.

Change-Id: I9305ba791dd43c9088a7bcbcc9af568ae127f60f
diff --git a/tests/scale/Voltha_Scale_Tests.robot b/tests/scale/Voltha_Scale_Tests.robot
index b794b20..8d3d471 100755
--- a/tests/scale/Voltha_Scale_Tests.robot
+++ b/tests/scale/Voltha_Scale_Tests.robot
@@ -133,14 +133,14 @@
     [Documentation]    Check that all the flows has been stored in the logical device
     [Tags]      flow-before   plot-voltha-flows-before
     # NOTE fail the test immediately if we're trying to check flows without provisioning them
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
     Wait for Logical Devices flows   ${workflow}    ${total_onus}    ${olt}    false
     ...     ${withEapol}    ${withDhcp}     ${withIgmp}    ${withLLDP}    ${timeout}
 
 Flows validation in VOLTHA Adapters before subscriber provisioning
     [Documentation]  Check that all flows has been store in devices of type openolt
     [Tags]      flow-before   plot-voltha-openolt-flows-before  only-me
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
     Wait for OpenOLT Devices flows   ${workflow}    ${total_onus}    ${olt}    false
     ...     ${withEapol}    ${withDhcp}     ${withIgmp}    ${withLLDP}
 
@@ -148,7 +148,7 @@
     [Documentation]    Check that all the flows has been acknowledged
     [Tags]      flow-before   plot-onos-flows-before
     # NOTE fail the test immediately if we're trying to check flows without provisioning them
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
 
     ${onos_devices}=    Compute Device IDs
     FOR     ${deviceId}     IN  @{onos_devices}
@@ -234,7 +234,7 @@
 Provision subscribers
     [Documentation]    Provision data plane flows for all the subscribers
     [Tags]      provision
-    Should Be Equal   ${enableSubscriberProvisioning}     true
+    Should Be Equal   ${enableSubscriberProvisioning}     true      Subscriber provisioning is not enabled
     ${onos_devices}=    Compute Device IDs
     FOR     ${olt}  IN  @{onos_devices}
         Provision all subscribers on device  ${ONOS_SSH_IP}    ${ONOS_SSH_PORT}    ${ONOS_SSH_IP}    ${ONOS_REST_PORT}  ${olt}
@@ -244,7 +244,7 @@
     [Documentation]    Check that all the flows has been stored in the logical device
     [Tags]      flow-after    plot-voltha-flows-after
     # NOTE fail the test immediately if we're trying to check flows without provisioning them
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
 
     Wait for Logical Devices flows   ${workflow}    ${total_onus}    ${olt}    true
     ...     ${withEapol}    ${withDhcp}     ${withIgmp}    ${withLLDP}    ${timeout}
@@ -252,7 +252,7 @@
 Flows validation in VOLTHA Adapters after subscriber provisioning
     [Documentation]  Check that all flows has been store in devices of type openolt
     [Tags]      flow-after   plot-voltha-openolt-flows-after    only-me
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
     Wait for OpenOLT Devices flows   ${workflow}    ${total_onus}    ${olt}    true
     ...     ${withEapol}    ${withDhcp}     ${withIgmp}    ${withLLDP}
 
@@ -260,7 +260,7 @@
     [Documentation]    Check that all the flows has been acknowledged
     [Tags]      flow-after    plot-onos-flows-after
     # NOTE fail the test immediately if we're trying to check flows without provisioning them
-    Should Be Equal   ${enableFlowProvisioning}     true
+    Should Be Equal   ${enableFlowProvisioning}     true    Flow provisioning is not enabled
 
     ${onos_devices}=    Compute Device IDs
     FOR     ${deviceId}     IN  @{onos_devices}
@@ -346,7 +346,7 @@
 *** Keywords ***
 Setup Suite
     [Documentation]    Setup test global variables, open an SSH connection to ONOS and starts a timer
-    Set Suite Variable    ${KUBECTL_CONFIG}    export KUBECONFIG=%{KUBECONFIG}
+    Set Suite Variable    ${KUBECTL_CONFIG}    %{KUBECONFIG}
     Set Suite Variable    ${VOLTCTL_CONFIG}    %{VOLTCONFIG}
 
     ${total_onus}=   Evaluate    ${olt} * ${pon} * ${onu}