The python3 modules listing was done before going to the root weboob git
dir.

The $'xxx' syntax is not standard shell syntax so it wasn't interpreted
correctly, causing pyflakes to spit a lot of errors.
This is after porting shebang to plain sh.

- use env(1) to found bash on the system
- remove bash dependency on few scripts

The solution to check if a version is installed is not enough for CI. We
often have python2 installed, but not onfigured.

This patch stops the behaviour to run both versions, a caller must now
call the script twice to check both pythons versions. It's not perfect,
but probably easier to understand

Also, fix missed warnings due to pyflakes.sh bug.
And ignore /deprecated/ in python3.

Since not all modules are Python3-compatible, don't emit warnings for
all. They should be declared in a dedicated file.
All modules are checked in Python2 though.

This will generate a lot of warnings on modules since they are not
python3-compatible yet.
Use the same flag for run_tests, and use python3 by default for weboob_lint.

For future Python 3 compatibility.

Use stream.isatty() instead.

close #1404

Signed-off-by: Christophe Lampin <weboob@lampin.net>

And use exec to capture the real return code.

They were not in the tools/pyflakes.sh runs

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.