Add mypy support

[chocoelho]

This PR resolves #198.

mypy doesn't output a code to identify the errors, it basically works with options you pass on the command line and the interface available to integrate with other tools accepts these arguments, so that's why it's not following the pattern of using disable messages but rather entries like disallow, no-check and so on.

These are some screenshots of it working:

Running only with mypy tool

VS Code output

.prospector.yaml configuration

[coveralls]

Coverage increased (+0.2%) to 58.676% when pulling 50cdd98 on vintasoftware:mypy-support into 1d993d4 on landscapeio:develop.

[coveralls]

Coverage increased (+0.04%) to 58.497% when pulling fe30c8a on vintasoftware:mypy-support into 1d993d4 on landscapeio:develop.

[coveralls]

Coverage increased (+0.1%) to 58.549% when pulling 56afa91 on vintasoftware:mypy-support into 1d993d4 on landscapeio:develop.

[coveralls]

Coverage increased (+0.1%) to 58.574% when pulling 1fc10d2 on vintasoftware:mypy-support into 1d993d4 on landscapeio:develop.

[pmatos]

Is there a reason this hasn't been merged?

[chocoelho]

@pmatos I guess it wasn't reviewed yet

[chocoelho]

This PR is going to take a little while longer to be merged. After syncing with the develop branch, I'm going to write a few more tests just to make sure it's properly integrated. But we're back on business :)

[twidi]

If prospector runs flake8, with its plugins, then the flake8-mypy should be enough instead of adding mypy support directly in prospector.

[fabianbuechler]

@twidi flake8 operates on single files, while mypy analyzes a complete codebase. The flake8-mypy plugin is therefore somewhat limited. Basically this note from the flake8-mypy page says it all:

Flake8 operates on unrelated files, it doesn’t perform full program analysis. In other words, it doesn’t follow imports. This is a curse and a blessing. We cannot find complex problems and the number of warnings we can safely show without risking false positives is lower. In return, we can provide useful warnings with great performance, usable for realtime editor integration.

[twidi]

Yes indeed, you're right.

[coveralls]

Pull Request Test Coverage Report for Build 591

• 2 of 49 (4.08%) changed or added relevant lines in 1 file are covered.
• 246 unchanged lines in 18 files lost coverage.
• Overall coverage increased (+0.5%) to 77.525%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
prospector/tools/mypy/init.py	2	49	4.08%

Files with Coverage Reduction	New Missed Lines	%
prospector/formatters/text.py	1	64.29%
prospector/encoding.py	5	66.67%
prospector/finder.py	6	83.59%
prospector/tools/pylint/linter.py	6	66.67%
prospector/message.py	8	79.66%
prospector/tools/pylint/collector.py	9	88.46%
prospector/tools/pep257/init.py	10	80.65%
prospector/config/init.py	10	80.21%
prospector/tools/pylint/indent_checker.py	11	80.77%
prospector/formatters/grouped.py	12	100.0%

Totals
Change from base Build 590:	0.5%
Covered Lines:	1497
Relevant Lines:	1931

---

💛 - Coveralls

[carlio]

Looks good to me.