With flake8, we can check for more issues and ignore those who are not
real issues.
This allowed me to find genuine errors in:
- modules/boursorama/pages/account_history.py
- modules/ing/pages/login.py
- weboob/tools/application/qt/qt.py
I left one in weboob/tools/browser/browser.py for the time being.
Some PEP8 fixes on other files.
This does not actually fix anything; the issue was that the page was
gzipped. However, since the code was not checking anything, it took me
some time to realize it. We now have at least one "BrokenPageError"
check.
