🔊 Add info about one reason for RuntimeError, which is otherwise difficult to catch

[tiangolo]

🔊 Add info about one reason for RuntimeError, which is otherwise difficult to catch

When there's a multiline error message in an assert, insert_assert can't find the frame, probably a quirk of Python. This adds a message showing what might be the problem.

Here's an example test that breaks with the RuntimeError:

def test_multiline_error_message(insert_assert):
    assert True, (
        "This error message has "
        "more than one line."
    )
    insert_assert(1)

The new error will show:

RuntimeError: insert_assert() was unable to find the frame from which it was called.

Sometimes this happens when there's an assert statement with a an error message with multiple lines, like: 

assert foo == bar, (
    'foo should be '
    'equal to bar'
)

You can try commenting out that assert statement while you run insert_assert() and then uncommenting it afterwards.

insert_assert was called with:
1

[codecov]

Codecov Report

Merging #149 (af33c65) into main (ec406ff) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #149   +/-   ##
=======================================
  Coverage   96.29%   96.29%           
=======================================
  Files           8        8           
  Lines         729      729           
  Branches      111      111           
=======================================
  Hits          702      702           
  Misses         21       21           
  Partials        6        6           

Files	Coverage Δ
devtools/pytest_plugin.py	88.13% <ø> (ø)

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