Problem:    Various pieces of code not covered by tests.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #8245)

Problem:    Python tests fail without the channel feature.
Solution:   Add a feature check. (Dominique Pellé, closes #8226)

Problem:    Crash when using Python list iterator.
Solution:   Increment the list reference count. (closes #7886)

Problem:    ml_get error when changing hidden buffer in Python.
Solution:   Block updating folds. (closes #7598)

Problem:    Python 3 test fails sometimes. (Christian Brabandt)
Solution:   Accept two SystemError messages.

Problem:    Python 3: non-utf8 character cannot be handled.
Solution:   Change the string decode. (Björn Linse, closes #1053)

Problem:    Various typos.
Solution:   Fix spelling mistakes. (closes #7494)

Problem:    Test for list and dict fails.
Solution:   Adjust for using an empty list/dict for a null one.

Problem:    With Python 3.9 some tests fail.
Solution:   Take into account the different error message. (James McCoy,
            closes #7210)

Problem:    Not all tests are executed on Github Actions.
Solution:   Copy "src" to "src2" earlier. Recognize "src2" in a couple more
            places.  Add two tests to the list of flaky tests. (Ken Takata,
            closes #6798)