Enable mypy review for pyshacl.cli:main and fix reported issues

[ajnelson-nist]

This patch updates the results of mypy --ignore-missing-imports, run only against /pyshacl/cli.py:

Count	Type-reviewed state
0	Current master branch state
40	Only designating main() -> None
0	Committed state

This patch updates the results of mypy --ignore-missing-imports, run against /pyshacl:

Count	Type-reviewed state
20	Current master branch state
61	Only designating main() -> None in cli.py
21	Committed state of cli.py
20	Committed state including main.py

[ajnelson-nist]

I've noticed type review hasn't passed for a while. So I included in this PR evidence that the number of issues at least doesn't grow, while the type-annotated coverage does.

[ajnelson-nist]

I checked running make dev ; make type-check in a fresh virtual environment, and it looks like the current Drone-reported failures against Python 3.8 are happening in this PR and on the master branch. And one of the type issues is something I don't quite understand with importlib, but it looks like #214 might influence that type issue's resolution.

Also, having caught up with the 0.24.0 release, this PR now appears to have no influence on the number of typing issues reported. So, the effect of the PR has become that type signatures are added.

[ajnelson-nist]

I believe after #223 is merged and this PR gets a catch-up merge, this PR will pass the type-checking Make target as it's currently written. There just seems to be the question of what the return type of pyshacl.cli.main should be.

[ajnelson-nist]

I believe after #223 is merged and this PR gets a catch-up merge, this PR will pass the type-checking Make target as it's currently written. There just seems to be the question of what the return type of pyshacl.cli.main should be.

Catch-up merge applied.

[ashleysommer]

Okay, I'm happy to merge this now

[ajnelson-nist]

Thank you!

[ashleysommer]

This is released now in PySHACL v0.26.0