Remove useless global vars / import

This removes a few import and global variables that are not used through
the code. That cleans things a little.

Change-Id: I7b30bb11e8ad3c2df01ca2107eff2444feed3fe2
Simplify common base exception prototype

It seems there's no gain in trying to be smarter and different from the
base Python Exception, so let's remove our custom code to be more
compatible and friendly with all Python versions.

Change-Id: I259783ef1f77c6661ea7dc2325605c8d6290b898
Merge "Remove useless global vars / import"
Refactors boolean returns

Return the boolean evaluation itself rather than
a boolean after evaluation

Change-Id: I6329d474c921e29eb3a690270de12d51cb863710
Remove vim header

No need to set tabstop 189 times, this can be set in your vimrc file
instead.  Also if set incorrectly gate (pep8 check) will catch your
mistakes.

Change-Id: Ic6f0c0ef94e8194a5c121598305d1ec3c74e4843
Unify different names between Python2/3 with six.moves

Some modules use different names in Python2 and Python3. Use six.moves
to make them work well in Python2 and Python3.
This is changes mapping:

six.moves      Python 2       Python 3
reduce         reduce()      functools.reduce()

Implements: blueprint make-python3-compatible
Change-Id: I97971f2ab40385bfc2c73ae7e8a7620c4d64a03c
Merge "Unify different names between Python2/3 with six.moves"
Merge "Remove vim header"