Pylint will use repo modules on PATH rather than its own

[anjsimmo]

Expected Behaviour:

• Pylint should never execute code within repo under analysis (as this could affect the analysis, or potentially even do something malicious)

Actual behaviour:

• When Pylint is run in root of a repo, modules in the repo will sometimes be loaded instead of Pylint's own imports! This usually causes Pylint to crash (but could potentially do anything).

Example:

• Root of project 39565135 contains a file called appdirs.py. When a Pylint dependency tries to import the appdir package, it mistakenly imports the local appdirs.py file instead.

INFO:root:../input/39565135
ERROR:root:['Traceback (most recent call last):', '  File "/usr/local/lib/python3.6/runpy.py", line 193, in _run_module_as_main', '    "__main__", mod_spec)', '  File "/usr/local/lib/python3.6/runpy.py", line 85, in _run_code', '    exec(code, run_globals)', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/__main__.py", line 7, in <module>', '    pylint.run_pylint()', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/__init__.py", line 23, in run_pylint', '    PylintRun(sys.argv[1:])', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/lint.py", line 1637, in __init__', '    linter.load_default_plugins()', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/lint.py", line 645, in load_default_plugins', '    checkers.initialize(self)', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/checkers/__init__.py", line 61, in initialize', '    register_plugins(linter, __path__[0])', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/utils/utils.py", line 218, in register_plugins', '    module = modutils.load_module_from_file(join(directory, filename))', '  File "/app/clean_env_py3/lib/python3.6/site-packages/astroid/modutils.py", line 280, in load_module_from_file', '    return load_module_from_modpath(modpath, path, use_sys)', '  File "/app/clean_env_py3/lib/python3.6/site-packages/astroid/modutils.py", line 241, in load_module_from_modpath', '    module = imp.load_module(curname, mp_file, mp_filename, mp_desc)', '  File "/usr/local/lib/python3.6/imp.py", line 235, in load_module', '    return load_source(name, filename, file)', '  File "/usr/local/lib/python3.6/imp.py", line 172, in load_source', '    module = _load(spec)', '  File "<frozen importlib._bootstrap>", line 684, in _load', '  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked', '  File "<frozen importlib._bootstrap_external>", line 678, in exec_module', '  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed', '  File "/app/clean_env_py3/lib/python3.6/site-packages/pylint/checkers/imports.py", line 40, in <module>', '    import isort', '  File "/app/clean_env_py3/lib/python3.6/site-packages/isort/__init__.py", line 25, in <module>', '    from . import settings  # noqa: F401', '  File "/app/clean_env_py3/lib/python3.6/site-packages/isort/settings.py", line 52, in <module>', "    if appdirs.system == 'darwin':", "AttributeError: module 'appdirs' has no attribute 'system'"]

Details:

https://github.com/PyCQA/pylint/blob/pylint-2.4.4/pylint/checkers/imports.py#L40

import isort

https://github.com/timothycrosley/isort/blob/4.3.21/isort/settings.py#L45

try:
    import appdirs
    if appdirs.system == 'darwin':
        appdirs.system = 'linux2'
except ImportError:
    appdirs = None

As appdirs package is not installed, the code is meant to catch an ImportError. Instead, it loads the local appdirs.py, which results in AttributeError: module 'appdirs' has no attribute 'system'" as it is a different module to what it expected.

[anjsimmo]

Additional details:

Was due to calling python -m pylint from within repo directories rather than using the pylint executable directly. This is fixed within #15.