Cfn-python-lint: jsonschema~=2.6 dependency causes DeprecationWarning under Python 3.7

[jmehnle]

cfn-lint version: 0.20.2

The jsonschema~=2.6 dependency causes a DeprecationWarning under Python 3.7:

  …/lib/python3.7/site-packages/jsonschema/compat.py:6: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
    from collections import MutableMapping, Sequence  # noqa

This was fixed in jsonschema 3.0.0. Can you please bump your jsonschema dependency to allow (or require) 3.0? (See also.)

[kddejong]

We should be able to update after https://github.com/awslabs/serverless-application-model/issues/922 is complete.

[kddejong]

This should be fixed in v0.22.0.