Also added code to show how to deal with #147

All performance tests still print to stderr, but do so in a py3 compatible way

Commandline was
autopep8 -j 8 --max-line-length 120 --in-place --recursive --exclude "*gitdb*,*async*" git/

Git utilizes multiple environment variables to control various
behaviours. Make sure to set LC_MESSAGES on a copy of the environment
instead of discarding any variables that may be set by the user or
default shell environment such as EDITOR.

Add test to assert that when overriding GIT_EDITOR via os.environ that
the modified value will be picked up by and git commands called.

W291 trailing whitespace

E201 whitespace after '('
E202 whitespace before ')'
E203 whitespace before ':'
E225 missing whitespace around operator
E226 missing whitespace around arithmetic operator
E227 missing whitespace around bitwise or shift operator
E228 missing whitespace around modulo operator
E231 missing whitespace after ','
E241 multiple spaces after ','
E251 unexpected spaces around keyword / parameter equals