The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
* E101: indentation contains mixed spaces and tabs
* E111: indentation is not a multiple of four
* E128: continuation line under-indented for visual indent
* E302: expected 2 blank lines, found 1
* W191: indentation contains tabs
Fixes:
* multiple statements on one line (colon) (E701)
* missing whitespace around arithmetic operator (E226)
* missing whitespace around operator (E225)
* closing bracket does not match visual indentation (E124)
* blank line contains whitespace (W293)
* continuation line missing indentation or outdented (E122)
* continuation line over-indented for hanging indent (E126)
* missing expected blank line (E301)
* trailing whitespace (W291)
* unexpected spaces around keyword / parameter equals (E251)
* whitespace after '(', '[' or '{' (E201)
* whitespace before ')', ']' or '}' (E202)
* whitespace before ',' or ':' (E203)
