Slightly adjust commands in Makefile

[drivendata]

Slightly adjust commands in Makefile

[pjbull]

Thanks for the report @Midnighter!

The changes to clean and lint seem good to me unless @isms had a thought as to why we would lint other directories. Also I'm a little wary of a rm -rf hidden in a Make command, so maybe we do both and remove the empty __pycache__ with rmdir instead.

WRT to requirements my reading of the doc is that requirements.txt is still where requirements will live by convention (including pinning certain versions). It seems that the constraints file is if you want to enforce certain versions across projects, for example, you can include one that will automate the checking that the project meets the requirements. However, it doesn't install the requirements. I'd leave as is.

[isms]

Thanks @Midnighter. Chiming in with some thoughts:

requirements: this is a nice point but I vote we revisit when constraints.txt is more widespread.

clean: no preference since the -delete flag is sort of rm -rfish and it shouldn't be a big deal with the pattern match.

lint concur, let's just lint src/