Create and install py.typed to advertise type annotations.

[ydirson]

This patch is successful at adding py.typed to bdist and wheel outputs. (There seems to be something to be done at RPM level to get it really installed but that's a different story).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (feeb478) 83.25% compared to head (00d5487) 83.25%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #123   +/-   ##
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  Coverage   83.25%   83.25%           
=======================================
  Files          22       22           
  Lines        3363     3363           
=======================================
  Hits         2800     2800           
  Misses        563      563           

Flag	Coverage Δ
unittest	83.25% <ø> (ø)

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[ydirson]

In the RPM packaging case, I suspected that the removal of setuptools_scm was to blame for the non-installed data file, so I also tried adding include xcp/py.typed to a MANIFEST.in, to no avail. Any idea appreciated. At least the standalone packaging does work.

Looks like python27.py would need some additional decls.

[bernhardkaindl]

@ydirson - Thank you, Yann!

For other reviewers: This adds an empty py.typed file which tells type checkers that this library has type annotations that they can use.

It only applies to type checkers and does not change regular run-time use in any way when type-checking is not used.