[v2 Downloader] requirements with dotted package names crash the library check

[calebj]

Command name

cog install calebj captcha

What cog is this command from?

Downloader

What were you expecting to happen?

Downloader should have pulled in the dependencies like normal using pip before installing the cog.

What actually happened?

Best guess is that since wheezy.captcha is a namespace package with a dot in the PyPI name, it's confusing the check. The wheezy module will import successfully when any subpackages are installed, but there is no package named just wheezy on PyPI. This doesn't happen when the package is already installed.

Exception in command 'cog install'
Traceback (most recent call last):
  File "/data/red/.local/lib/python3.5/site-packages/discord/ext/commands/core.py", line 50, in wrapped
    ret = yield from coro(*args, **kwargs)
  File "/data/red/cogs/downloader.py", line 397, in _install
    install_cog = await self.install(repo_name, cog, notify_reqs=True)
  File "/data/red/cogs/downloader.py", line 447, in install
    requirements = [r for r in requirements
  File "/data/red/cogs/downloader.py", line 448, in <listcomp>
    if not self.is_lib_installed(r)]
  File "/data/red/cogs/downloader.py", line 530, in is_lib_installed
    return bool(find_spec(name))
  File "/usr/lib/python3.5/importlib/util.py", line 88, in find_spec
    parent = __import__(parent_name, fromlist=['__path__'])
ImportError: No module named 'wheezy'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/data/red/.local/lib/python3.5/site-packages/discord/ext/commands/bot.py", line 846, in process_commands
    yield from command.invoke(ctx)
  File "/data/red/.local/lib/python3.5/site-packages/discord/ext/commands/core.py", line 634, in invoke
    yield from ctx.invoked_subcommand.invoke(ctx)
  File "/data/red/.local/lib/python3.5/site-packages/discord/ext/commands/core.py", line 374, in invoke
    yield from injected(*ctx.args, **ctx.kwargs)
  File "/data/red/.local/lib/python3.5/site-packages/discord/ext/commands/core.py", line 54, in wrapped
    raise CommandInvokeError(e) from e
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: ImportError: No module named 'wheezy'

How can we reproduce this issue?

1. Attempt to install Captcha from my cog repo's develop branch
2. Cry. Cry a lot.

[Twentysix26]

>>> find_spec("wheezy.captcha")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\...\Python36-32\lib\importlib\util.py", line 88, in find_spec
    parent = __import__(parent_name, fromlist=['__path__'])
ModuleNotFoundError: No module named 'wheezy'

I'm getting a different type of exception. Might be worth catching both?

[calebj]

It's already caught, since ModuleNotFoundError is a subclass of ImportError added in 3.6.