bandit hangs if current directory contains __init__.py

[Calvin Li]

Hi!

The function bandit.core.utils.get_module_qualname_from_path() examines the filepath from right-to-left looking for a directory without an __init__.py. If bandit is called using relative paths inside a directory that contains a __init__.py, this function enters an infinite loop.

Example:

```
.:
__init__.py test/

./test:
__init__.py test.py
```

Calling bandit with `bandit test/test.py` leads to an infinite loop. `bandit ./test/test.py` gives the expected result (with detected qualname `test.test`).

The following diff to get_module_qualname_from_path() appears to fix the issue:

```
- while head not in ['/', '.']:
+ while head not in ['/', '.', '']:
```

Thanks

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/537242

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jeremy Liu (<email address hidden>) on branch: master
Review: https://review.openstack.org/537242
Reason: dup

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/533382
Committed: https://git.openstack.org/cgit/openstack/bandit/commit/?id=90f031c9735639a5049f742c8f5cf4eb8fc8b055
Submitter: Zuul
Branch: master

commit 90f031c9735639a5049f742c8f5cf4eb8fc8b055
Author: Tin Lam <email address hidden>
Date: Sat Jan 13 21:58:15 2018 -0600

    Fix infinite loop issue

    Running bandit using relative paths inside a subdirectory when the current
    directory contains __init__.py causes bandit to be stuck in an infinite
    loop.

    Co-Authored-By: Calvin Li
    Closes-Bug: #1743042
    Change-Id: I247108c1365847134ee561073ea0eb43c57b54cc