Automated tests are not passing under Python 3.8

[bolinfest]

At the time of this writing, although the Travis-CI badge on the README.md for this project is green, if you visit the corresponding https://travis-ci.org/github/cmark-gfm, it says "We couldn't find the owner cmark-gfm." There have not been any commits to this repo in awhile, so I guess the Travis build has not run in awhile, either? Or someone needs to update GitHub's credit card registered with Travis-CI?

On master (currently 85d8952), I ran make test locally on both a Mac and Linux machine (with Python 3.8.6) and both had quite a few failures:

Running tests...
Test project /data/users/mbolin/cmark-gfm/build
      Start  1: api_test
 1/13 Test  #1: api_test ...............................   Passed    0.13 sec
      Start  2: html_normalization
 2/13 Test  #2: html_normalization .....................***Failed    0.10 sec
      Start  3: spectest_library
 3/13 Test  #3: spectest_library .......................   Passed    0.09 sec
      Start  4: pathological_tests_library
 4/13 Test  #4: pathological_tests_library .............   Passed    3.84 sec
      Start  5: roundtriptest_library
 5/13 Test  #5: roundtriptest_library ..................***Failed    0.12 sec
      Start  6: entity_library
 6/13 Test  #6: entity_library .........................   Passed    0.08 sec
      Start  7: spectest_executable
 7/13 Test  #7: spectest_executable ....................   Passed    1.11 sec
      Start  8: smartpuncttest_executable
 8/13 Test  #8: smartpuncttest_executable ..............   Passed    0.09 sec
      Start  9: extensions_executable
 9/13 Test  #9: extensions_executable ..................   Passed    0.11 sec
      Start 10: roundtrip_extensions_executable
10/13 Test #10: roundtrip_extensions_executable ........***Failed    0.09 sec
      Start 11: option_table_prefer_style_attributes
11/13 Test #11: option_table_prefer_style_attributes ...***Failed    0.07 sec
      Start 12: option_full_info_string
12/13 Test #12: option_full_info_string ................***Failed    0.07 sec
      Start 13: regressiontest_executable
13/13 Test #13: regressiontest_executable ..............   Passed    0.10 sec

62% tests passed, 5 tests failed out of 13

Total Test time (real) =   6.00 sec

The following tests FAILED:
	  2 - html_normalization (Failed)
	  5 - roundtriptest_library (Failed)
	 10 - roundtrip_extensions_executable (Failed)
	 11 - option_table_prefer_style_attributes (Failed)
	 12 - option_full_info_string (Failed)
Errors while running CTest
make: *** [test] Error 8

I looked into the first failure and it was due to a deprecation in the Python standard library introduced in 3.8 and I sent out a pull request for that: #216. This change seems to fix all the tests.

[phillmv]

This got fixed! Thanks for making note of it and submitting a PR.