bears/python: Add PyFlakesBear

Closes coala#825

bears/python/PyFlakesBear.py

@@ -0,0 +1,30 @@
+from coalib.bearlib.abstractions.Linter import linter
+from coalib.bears.requirements.PipRequirement import PipRequirement
+from coalib.results.RESULT_SEVERITY import RESULT_SEVERITY
+
+
+@linter(executable='pyflakes',
+        use_stderr=True,
+        output_format='regex',
+        output_regex=r'(?P<filename>.*):(?P<line>\d+):'
+                     r'[(?P<column>\d*):|?]*(?P<severity>)\s(?P<message>.*)\n',
+        severity_map={
+            '': RESULT_SEVERITY.INFO
+        })
+class PyFlakesBear:
+    """
+    Checks Python files for errors using ``pyflakes``.
+
+    See https://github.com/PyCQA/pyflakes for more info.
+    """
+    LANGUAGES = {'Python', 'Python 3'}
+    REQUIREMENTS = {PipRequirement('pyflakes', '1.2.*')}
+    AUTHORS = {'The coala developers'}
+    AUTHORS_EMAILS = {'[email protected]'}
+    LICENSE = 'AGPL-3.0'
+    ASCIINEMA_URL = 'https://asciinema.org/a/92503'
+    CAN_DETECT = {'Syntax', 'Unused Code', 'Undefined Element'}
+
+    @staticmethod
+    def create_arguments(filename, file, config_file):
+        return filename,

requirements.txt

@@ -26,6 +26,7 @@ pyyaml~=3.12
 vulture~=0.10
 bandit~=1.2
 nbformat>=4.1
+pyflakes~=1.2.0
 scspell3k~=2.0
 mypy-lang~=0.4
 rstcheck~=2.2

tests/python/PyFlakesBearTest.py

@@ -0,0 +1,15 @@
+from bears.python.PyFlakesBear import PyFlakesBear
+from tests.LocalBearTestHelper import verify_local_bear
+
+good_file = """
+print("Hi")
+"""
+
+bad_file = """
+import os
+print("Hi")
+"""
+
+PyFlakesBear = verify_local_bear(PyFlakesBear,
+                                 valid_files=(good_file,),
+                                 invalid_files=(bad_file,))