Change KeyType to use Any

[mxr]

This is needed to correctly type lookups for keys that use UTCDateTimeAttribute, and future-proof further changes

[garrettheel]

Generally looks good to me, will just have to figure out what the type error is

[mxr]

The command "pytest --cov-report term-missing --cov=pynamodb tests" exited with 0.
11.07s$ if [[ "$TRAVIS_PYTHON_VERSION" == "3.7" ]]; then mypy .; fi
pynamodb/_compat.py:13: error: Too few arguments for "load_module" of "InspectLoader"
Found 1 error in 1 file (checked 46 source files)
The command "if [[ "$TRAVIS_PYTHON_VERSION" == "3.7" ]]; then mypy .; fi" exited with 1.

I suspect this is not related to my PR but I can dig around and check on master

[ikonst]

Perhaps we can type it to be Any? Otherwise it can still conflict with other custom attributes whose types we cannot foresee.

[mxr]

Works for me

[garrettheel]

#763 to fix tests

[mxr]

CI is green! @ikonst could you merge this when you have a chance? ty

[ikonst]

Thanks @mxr !

[mxr]

Thank you!!