pylint crashes when "with ... as" is used in an enum

[martimlobao]

Steps to reproduce

1. Create test.py:

import enum

class Error(enum.Enum):
    Foo = "foo"
    Bar = "bar"
    with "error" as err:
        pass

2. Run pylint test.py.

Current behavior

An IndexError exception is raised and pylint crashes:

$ pylint test.py
************* Module test
test.py:1:0: C0114: Missing module docstring (missing-module-docstring)
test.py:4:0: C0115: Missing class docstring (missing-class-docstring)
Traceback (most recent call last):
  File "/Users/me/.pyenv/versions/clean/bin/pylint", line 11, in <module>
    sys.exit(run_pylint())
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/__init__.py", line 23, in run_pylint
    PylintRun(sys.argv[1:])
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/lint.py", line 1731, in __init__
    linter.check(args)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/lint.py", line 1004, in check
    self._do_check(files_or_modules)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/lint.py", line 1165, in _do_check
    self.check_astroid_module(ast_node, walker, rawcheckers, tokencheckers)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/lint.py", line 1252, in check_astroid_module
    walker.walk(ast_node)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/utils/ast_walker.py", line 74, in walk
    callback(astroid)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/checkers/classes.py", line 755, in visit_classdef
    self._check_bases_classes(node)
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/checkers/classes.py", line 1537, in _check_bases_classes
    if class_is_abstract(node):
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/pylint/checkers/utils.py", line 929, in class_is_abstract
    for method in node.methods():
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/astroid/scoped_nodes.py", line 2547, in methods
    for meth in astroid.mymethods():
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/astroid/scoped_nodes.py", line 2559, in mymethods
    for member in self.values():
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/astroid/scoped_nodes.py", line 276, in values
    return [self[key] for key in self.keys()]
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/astroid/scoped_nodes.py", line 276, in <listcomp>
    return [self[key] for key in self.keys()]
  File "/Users/me/.pyenv/versions/3.6.6/envs/clean/lib/python3.6/site-packages/astroid/scoped_nodes.py", line 252, in __getitem__
    return self.locals[item][0]
IndexError: list index out of range

Expected behavior

pylint should not crash.

pylint --version output

astroid 2.3.3
Python 3.6.6 (default, Feb 12 2019, 20:41:17) 
[GCC 4.2.1 Compatible Apple LLVM 10.0.0 (clang-1000.10.44.4)]