modulefinder skips nested modules with same name as top-level bad module

[rdb]

BPO	35376
Nosy	@ncoghlan, @ericsnowcurrently, @rdb
PRs	bpo-35376: Fix modulefinder skipping some nested modules #10895 bpo-35936: Updates to modulefinder #11787
Files	patch.diff: Patch (made against 3.6 branch)

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-04-07.08:06:56.872>
created_at = <Date 2018-12-02.15:00:55.410>
labels = ['3.8', 'type-bug', 'library']
title = 'modulefinder skips nested modules with same name as top-level bad module'
updated_at = <Date 2019-04-07.08:06:56.871>
user = 'https://github.com/rdb'

bugs.python.org fields:

activity = <Date 2019-04-07.08:06:56.871>
actor = 'ncoghlan'
assignee = 'none'
closed = True
closed_date = <Date 2019-04-07.08:06:56.872>
closer = 'ncoghlan'
components = ['Library (Lib)']
creation = <Date 2018-12-02.15:00:55.410>
creator = 'rdb'
dependencies = []
files = ['47968']
hgrepos = []
issue_num = 35376
keywords = ['patch']
message_count = 3.0
messages = ['330883', '331366', '339563']
nosy_count = 4.0
nosy_names = ['jvr', 'ncoghlan', 'eric.snow', 'rdb']
pr_nums = ['10895', '11787']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue35376'
versions = ['Python 3.8']

[rdb]

If modulefinder finds a nested module import (eg. 'import a.b.c') while there is a top-level module with the same name (eg. 'c') that failed to import and got added to the badmodules list, it will skip it entirely without even trying to import it.

This has a trivial fix (attached). The right thing to do is clearly to check it by fqname in the badmodules dict since that's also what it expects in other locations.

I can make a PR as soon as my CLA gets validated, if that is more convenient. (Which branch should I make the PR against?)

[brettcannon]

PRs should always be against 'master' unless the issue is already fixed there.

[ncoghlan]

Fixed for Python 3.8 via the patch for bpo-35936. We won't be backporting that patch as it also migrates modulefinder from the deprecated imp API to the supported importlib one, and is hence considered overly intrusive for a bug fix release.