This relies on two things:
1. Properly configuring flake8-import-order to use that style
2. Properly configuring flake8-import-order to know that flake8 is our
application name.
This allows us to handle --show-source in our formatters by default.
This also adds the physical line information to the Error class instead
of passing it to is_inline_ignored. This allows us to avoid using
linecache in our formatters.
