Fixes CVE CI job

[zenmonkeykstop]

Status

Ready for review

Description of Changes

Fixes #4424

Changes proposed in this pull request:
In Makefile bandit target, blacklists bandit 1.6.0 due to directory exclusion bug, installs latest pip. (A fix for the directory exclusion bug as mentioned here: PyCQA/bandit#488 will be forthcoming in v1.6.1 - it shouldn't be necessary to roll back the Makefile change when this happens.)

Testing

This should fix the CI CVE check job. To test it locally, check out the branch and run make bandit

Deployment

No deployment, CI fix only

[eloquence]

Works locally for me:

Run started:2019-05-10 16:35:37.320497

Test results:
	No issues identified.

Code scanned:
	Total lines of code: 8640
	Total lines skipped (#nosec): 7

Run metrics:
	Total issues (by severity):
		Undefined: 0
		Low: 306
		Medium: 0
		High: 0
	Total issues (by confidence):
		Undefined: 0
		Low: 0
		Medium: 0
		High: 306
Files skipped (1):
	./journalist_gui/journalist_gui/SecureDropUpdater.py (syntax error while parsing AST from file)

[conorsch]

Works for me locally, and CI is passing! 👍