Coding style cleanup

Fix the following issues reported by pylint:

C0321: More than one statement on a single line
W0622: Redefining built-in 'name'
W0612: Unused variable 'name'
W0613: Unused argument 'name'
W0102: Dangerous default value 'value' as argument
W0105: String statement has no effect

Also fixed a few cases of inconsistent indentation.

Change-Id: Ie0db839e7c57d576cff12d8c055fe87030d00744
diff --git a/error.py b/error.py
index 48e3189..783ab7d 100644
--- a/error.py
+++ b/error.py
@@ -85,8 +85,8 @@
      repo or manifest repositories.  In this special case we must
      use exec to re-execute repo with the new code and manifest.
   """
-  def __init__(self, extra_args=[]):
-    self.extra_args = extra_args
+  def __init__(self, extra_args=None):
+    self.extra_args = extra_args or []
 
 class HookError(Exception):
   """Thrown if a 'repo-hook' could not be run.