Typo in the py_str function

[deontologician]

Looks like maybe_unstr is defined, but maybe_str is used. In python_tests all exceptions are discarded though, so a few places where there is a valid ot value aren't found by the converter

[deontologician]

Specifically, I got a difference on these:

regression/4146.yaml test #1
    should be : "{'created': 1}"
    got       : None
regression/3637.yaml test #2
    should be : "{'id': 0.0, 'value': 'abc'}"
    got       : None
regression/3637.yaml test #3
    should be : "{'id': 0.0, 'value': 'abc'}"
    got       : None
meta/table.yaml test #53
    should be : "{'inserted': 4}"
    got       : None
changefeeds/point.yaml test #31
    should be : "{'skipped': 0, 'replaced': 0, 'errors': 0, 'deleted': 0, 'unchanged': 0, 'inserted': 1}"
    got       : None

[AtnNn]

Does changing maybe_unstr to maybe_str fix the issue?

I don't recognize that output format. Where is it from?

[deontologician]

The typo is hiding some other bugs. The format is just a comparison I did between the original version and one that fixes that particular issue