Fix issue #453 jinja2 template select_autoescape when using jinja2.select_autoescape

[kinow]

Hi,

I added a test to reproduce what was reported in #453 . Running the test first, without the patch, gives:

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    b'Traceback (most recent call last):'
    b'  File "/home/kinow/Development/python/workspace/bandit/tests/functional/test_functional.py", line 504, in test_jinja2_templating'
    b"    self.check_example('jinja2_templating.py', expect)"
    b'  File "/home/kinow/Development/python/workspace/bandit/tests/functional/test_functional.py", line 86, in check_example'
    b'    self.assertDictEqual(expect, result)'
    b'  File "/home/kinow/Development/python/anaconda3/lib/python3.7/site-packages/unittest2/case.py", line 1128, in assertDictEqual'
    b'    self.fail(self._formatMessage(msg, standardMsg))'
    b'  File "/home/kinow/Development/python/anaconda3/lib/python3.7/site-packages/unittest2/case.py", line 690, in fail'
    b'    raise self.failureException(msg)'
    b"AssertionError: {'SEV[51 chars]GH': 5}, 'CONFIDENCE': {'UNDEFINED': 0, 'LOW':[23 chars]: 3}} != {'SEV[51 chars]GH': 6}, 'CONFIDENCE': {'UNDEFINED': 0, 'LOW':[23 chars]: 3}}"
    b"- {'CONFIDENCE': {'HIGH': 3, 'LOW': 0, 'MEDIUM': 2, 'UNDEFINED': 0},"
    b'?                                                ^'
    b''
    b"+ {'CONFIDENCE': {'HIGH': 3, 'LOW': 0, 'MEDIUM': 3, 'UNDEFINED': 0},"
    b'?                                                ^'
    b''
    b"-  'SEVERITY': {'HIGH': 5, 'LOW': 0, 'MEDIUM': 0, 'UNDEFINED': 0}}"
    b'?                       ^'
    b''
    b"+  'SEVERITY': {'HIGH': 6, 'LOW': 0, 'MEDIUM': 0, 'UNDEFINED': 0}}"
    b'?                       ^'
    b''
    b''


======
Totals
======
Ran: 244 tests in 4.4894 sec.
 - Passed: 243
 - Skipped: 0
 - Expected Fail: 0
 - Unexpected Success: 0
 - Failed: 1

Hopefully Travis CI will report that this patch produced no failures in the tests. I avoided trying to check if the jinja2 module was aliased, as I think we would have to look at the Context imports, store in a variable what was the method, and add yet another if for that? But if there's a simpler way or if necessary, happy to update this pull request.

Cheers
Bruno

[kinow]

Aarrgh. Had a hard time fixing flake8 style issues, sorry. Sometimes it can be quite tricky to format everything under 80 columns :-) Rebased.

[ericwb]

LGTM

[kinow]

Thanks for reviewing and sorting out formatting and last touches to get it merged, @ericwb 👍

[mportesdev]

@ericwb Hi Eric, I think issue #711 and PR #903 can also be closed after this merge.