errors: remove trailing "!" from some error messages for consistency
Some types of exceptions had a trailing "!" printed after the message
from the exception itself. I guess some of these errors seem a little
more severe (?), but it seems more likely that the inconsistency was
just an oversight.
Differential Revision: https://phab.mercurial-scm.org/D9378
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true