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

There is more work to do though, as many imports are still incorrect.
Also, there are still print statements

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

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

E301 expected 1 blank line, found 0
E302 expected 2 blank lines, found 1
E303 too many blank lines (n)

W191 indentation contains tabs
E221 multiple spaces before operator
E222 multiple spaces after operator
E225 missing whitespace around operator
E271 multiple spaces after keyword
W292 no newline at end of file
W293 blank line contains whitespace
W391 blank line at end of file

The latter will break code that assumes it will get a string.