Fix log message formatting during exception handling

[abn]

This fixes the log message by ensuring we only log the EntryPoint name. The root issue can be reproduced independently as shown below.

$ python -c 'from importlib.metadata import EntryPoint; "%s" % EntryPoint(name="name", value="value", group="group")'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: not all arguments converted during string formatting

Related to: #411 pypa/twine#552 python-poetry/poetry#1719

The above issues resolved the exception root causes but never fixed the second exception thrown from the exception handling block.

[jaraco]

Thanks for this. This undesirable behavior was an unfortunate consequence of the fact that EntryPoint is iterable (a namedtuple), so %s string formatting tries to iterate it, rather than invoking repr on the object. I'll want to decide if rendering the entire entry point was the intended behavior and should be retained or if rendering just the name is sufficient.

[jaraco]

Seeing as that code didn't change with either entrypoints replacement (a9fe227, 0028d73), I think rendering the whole entrypoint is what's intended here.