Unhelpful click errors in test suite due to fallback main() function.

[bnavigator]

"Bug reports" such as #2243 / #2270 are not very indicative because the displayed error message is not instructive at all:

>       return cli.name or "root"
E       AttributeError: 'function' object has no attribute 'name'

/usr/lib/python3.8/site-packages/click/testing.py:195: AttributeError

I got the same error in my own packaging efforts and could not make any sense out of it until I discovered, that the code in init.py

httpx/httpx/__init__.py

Lines 47 to 59 in 3aa4410

	try:
	from ._main import main
	except ImportError: # pragma: nocover
	def main() -> None: # type: ignore
	import sys
	print(
	"The httpx command line client could not run because the required "
	"dependencies were not installed.\nMake sure you've installed "
	"everything with: pip install 'httpx[cli]'"
	)
	sys.exit(1)

totally hides the real problem.

After replacing the try:, except: Block with a plain import of main, the resulting backtrace showed me that there was a packaging error in rich:

[    7s] ImportError while loading conftest '/home/abuild/rpmbuild/BUILD/httpx-0.23.0/tests/conftest.py'.
[    7s] tests/conftest.py:20: in <module>
[    7s]     from httpx import URL
[    7s] httpx/__init__.py:48: in <module>
[    7s]     from ._main import main
[    7s] httpx/_main.py:10: in <module>
[    7s]     import rich.console
[    7s] /usr/lib/python3.8/site-packages/rich/console.py:53: in <module>
[    7s]     from ._log_render import FormatTimeCallable, LogRender
[    7s] /usr/lib/python3.8/site-packages/rich/_log_render.py:5: in <module>
[    7s]     from .text import Text, TextType
[    7s] /usr/lib/python3.8/site-packages/rich/text.py:5: in <module>
[    7s]     from rich.emoji import EmojiVariant
[    7s] /usr/lib/python3.8/site-packages/rich/emoji.py:4: in <module>
[    7s]     from .jupyter import JupyterMixin
[    7s] /usr/lib/python3.8/site-packages/rich/jupyter.py:7: in <module>
[    7s]     from .segment import Segment
[    7s] /usr/lib/python3.8/site-packages/rich/segment.py:19: in <module>
[    7s]     from .cells import (
[    7s] /usr/lib/python3.8/site-packages/rich/cells.py:6: in <module>
[    7s]     from ._lru_cache import LRUCache
[    7s] /usr/lib/python3.8/site-packages/rich/_lru_cache.py:8: in <module>
[    7s]     from typing_extensions import OrderedDict
[    7s] E   ModuleNotFoundError: No module named 'typing_extensions'

I suspect the original reporter had a similar problem, as this was indeed some problem of rich: Textualize/rich#2386

The fallback should be made more robust for a proper error message, when the Click Test runner tries to run the command.