pylint with astroid 2.5 raises an exception when checking aiohttp or any library that depends on aiohttp

[danking]

Steps to reproduce

1. In a fresh environment, pip3 install pylint
2. In that environment, pylint aiohttp

Current behavior

Traceback (most recent call last):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 34, in cached
    return cache[func]
KeyError: <bound method ClassDef.slots of <ClassDef.AbstractResource l.76 at 0x7f83c4b42490>>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/dking/miniconda3/envs/garbage/bin/pylint", line 8, in <module>
    sys.exit(run_pylint())
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/__init__.py", line 22, in run_pylint
    PylintRun(sys.argv[1:])
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/run.py", line 349, in __init__
    linter.check(args)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 863, in check
    self.get_ast, self._iterate_file_descrs(files_or_modules)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 896, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 922, in _check_file
    check_astroid_module(ast_node)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 1055, in check_astroid_module
    ast_node, walker, rawcheckers, tokencheckers
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 1099, in _check_astroid_module
    walker.walk(ast_node)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 75, in walk
    self.walk(child)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 75, in walk
    self.walk(child)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/utils/ast_walker.py", line 72, in walk
    callback(astroid)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/checkers/typecheck.py", line 1037, in visit_assign
    self._check_assignment_from_function_call(node)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/checkers/typecheck.py", line 1047, in _check_assignment_from_function_call
    function_node = safe_infer(node.value.func)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/pylint/checkers/utils.py", line 1143, in safe_infer
    value = next(infer_gen)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/node_classes.py", line 365, in infer
    yield from self._infer(context, **kwargs)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 134, in raise_if_nothing_inferred
    yield next(generator)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 98, in wrapped
    res = next(generator)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/bases.py", line 136, in _infer_stmts
    for inferred in stmt.infer(context=context):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/node_classes.py", line 379, in infer
    for i, result in enumerate(generator):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 134, in raise_if_nothing_inferred
    yield next(generator)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 98, in wrapped
    res = next(generator)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/bases.py", line 136, in _infer_stmts
    for inferred in stmt.infer(context=context):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/node_classes.py", line 379, in infer
    for i, result in enumerate(generator):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 134, in raise_if_nothing_inferred
    yield next(generator)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 95, in wrapped
    generator = _func(node, context, **kwargs)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/inference.py", line 273, in infer_import_from
    module = self.do_import_module()
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/mixins.py", line 100, in do_import_module
    modname, level=level, relative_only=level and level >= 1
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 646, in import_module
    return MANAGER.ast_from_module_name(absmodname)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/manager.py", line 191, in ast_from_module_name
    return self.ast_from_file(found_spec.location, modname, fallback=False)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/manager.py", line 100, in ast_from_file
    return AstroidBuilder(self).file_build(filepath, modname)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/builder.py", line 139, in file_build
    return self._post_build(module, encoding)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/builder.py", line 159, in _post_build
    self.delayed_assattr(delayed)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/builder.py", line 235, in delayed_assattr
    if not _can_assign_attr(inferred, node.attrname):
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/builder.py", line 60, in _can_assign_attr
    slots = node.slots()
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/decorators.py", line 36, in cached
    cache[func] = result = func(*args, **kwargs)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 2838, in slots
    slots = list(grouped_slots())
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 2823, in grouped_slots
    for cls in self.mro()[:-1]:
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 2909, in mro
    return self._compute_mro(context=context)
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 2898, in _compute_mro
    unmerged_mro = list(clean_duplicates_mro(unmerged_mro, self, context))
  File "/Users/dking/miniconda3/envs/garbage/lib/python3.7/site-packages/astroid/scoped_nodes.py", line 114, in clean_duplicates_mro
    context=context,
astroid.exceptions.DuplicateBasesError: Duplicates found in MROs (AbstractResource), (_GenericAlias, _Final, object), (_GenericAlias, _Final, object), (_GenericAlias, _GenericAlias) for <ClassDef.AbstractResource l.76 at 0x7f83c4b42490>.

Expected behavior

No exceptions.

pylint --version output

(garbage) # pylint --version  
zsh: /usr/local/bin/pylint: bad interpreter: /usr/local/opt/python/bin/python3.7: no such file or directory
pylint 2.6.0
astroid 2.5
Python 3.7.9 (default, Aug 31 2020, 07:22:35) 
[Clang 10.0.0 ]

[cdce8p]

This issue is similar to #4093 and pylint-dev/astroid#905
I've already opened a PR to address it for the next (bugfix) release: pylint-dev/astroid#910

[cdce8p]

@danking Pylint 2.7.2 has just been released. That should have fixed the issue. Just to be sure, can you test if everything works?

[postlund]

Works for me! 👍