##### SUMMARY
In ansible-collections/community.general#49 I am adding a new module_utils directory, a Python module in there, and at the same time use that new module_utils in some Ansible modules.

Example commit: 7341b4a1e48bf6e652dd5f70c5a5a5808d73de7e
CI run: https://app.shippable.com/github/ansible-collections/community.general/runs/172/summary/console

All CI nodes (at least the ones I randomly checked) fail with the same error:
```
00:45 Detected changes in 4 file(s).
00:45 plugins/module_utils/compat/__init__.py
00:45 plugins/module_utils/compat/ipaddress.py
00:45 plugins/modules/cloud/scaleway/scaleway_security_group_rule.py
00:45 plugins/modules/net_tools/hetzner_firewall.py
00:45 Analyzing python module_utils imports...
00:59 WARNING: No imports found which use the "ansible_collections.community.general.plugins.module_utils.f5_utils" module_util.
00:59 WARNING: No imports found which use the "ansible_collections.community.general.plugins.module_utils.network.aos.aos" module_util.
00:59 WARNING: No imports found which use the "ansible_collections.community.general.plugins.module_utils.network.f5.iworkflow" module_util.
00:59 WARNING: No imports found which use the "ansible_collections.community.general.plugins.module_utils.network.panos.panos" module_util.
00:59 Processed 116 python module_utils in 13 second(s).
00:59 Traceback (most recent call last):
00:59   File "/root/venv/bin/ansible-test", line 28, in <module>
00:59     main()
00:59   File "/root/venv/bin/ansible-test", line 24, in main
00:59     cli_main()
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/cli.py", line 173, in main
00:59     args.func(config)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/sanity/__init__.py", line 85, in command_sanity
00:59     changes = get_changes_filter(args)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/executor.py", line 1493, in get_changes_filter
00:59     changes = categorize_changes(args, paths, args.command)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/classification.py", line 89, in categorize_changes
00:59     dependent_paths = mapper.get_dependent_paths(path)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/classification.py", line 236, in get_dependent_paths
00:59     unprocessed_paths = set(self.get_dependent_paths_non_recursive(path))
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/classification.py", line 258, in get_dependent_paths_non_recursive
00:59     paths = self.get_dependent_paths_internal(path)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/classification.py", line 273, in get_dependent_paths_internal
00:59     return self.get_python_module_utils_usage(path)
00:59   File "/root/venv/lib/python2.7/site-packages/ansible_test/_internal/classification.py", line 306, in get_python_module_utils_usage
00:59     return sorted(self.python_module_utils_imports[name])
00:59 KeyError: u'ansible_collections.community.general.plugins.module_utils.compat'
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-test

##### ANSIBLE VERSION
```paste below
devel
```

"""Return the classification for the given path using rules specific to collections."""
        result = self._classify_common(path)
        if result is not None:
            return result
        return None
    def _classify_ansible(self, path):  
        """Return the classification for the given path using rules specific to Ansible."""
        if path.startswith('test/units/compat/'):
            return {
                'units': 'test/units/',
            }
        result = self._classify_common(path)
        if result is not None:
            return result
        dirname = os.path.dirname(path)
        filename = os.path.basename(path)
        name, ext = os.path.splitext(filename)
        minimal = {}
        if path.startswith('bin/'):
            return all_tests(self.args)  
        if path.startswith('changelogs/'):
            return minimal
        if path.startswith('contrib/'):
            return {
                'units': 'test/units/contrib/'
            }
        if path.startswith('docs/'):