ImageDimensionBear: Add image dimension bear

Added ImageDimensionBear.py in bears/general, that runs
the gem img_checker to see if images follow provided
dimensions.
Also added unittest for the bear, ImageDimensionBearTest.py
in tests/general

Gemfile

@@ -7,3 +7,4 @@ gem 'scss_lint', require: false# require flag is necessary https://github.com/br
 gem "reek"
 gem "puppet-lint"
 gem "csvlint"
+gem "img_checker"

bears/general/ImageDimensionBear.py

@@ -0,0 +1,57 @@
+import os
+import yaml
+import shutil
+
+from coalib.bears.GlobalBear import GlobalBear
+from coalib.results.Result import Result
+from coalib.results.RESULT_SEVERITY import RESULT_SEVERITY
+from dependency_management.requirements.GemRequirement import GemRequirement
+from dependency_management.requirements.PipRequirement import PipRequirement
+from sarge import run, Capture
+
+
+class ImageDimensionBear(GlobalBear):
+    """
+    Checks the dimension of an image.
+
+    More information is available at <github.com/Abhi2424shek/img_checker>
+    """
+
+    AUTHORS = {'The coala developers'}
+    AUTHORS_EMAILS = {'[email protected]'}
+    REQUIREMENTS = {GemRequirement(' img_checker'),
+                    PipRequirement('pyyaml', '3.12')}
+    LICENSE = 'AGPL-3.0'
+    CAN_FIX = {'Image Dimension'}
+
+    @classmethod
+    def check_prerequisites(cls):
+        if shutil.which('img_checker') is None:
+            return 'img_checker is not installed.'
+        return True
+
+    def run(self,
+            image_file,
+            width,
+            height):
+
+        with open('img_config.yml', 'w') as yaml_file:
+            config = [{'directory': image_file,
+                       'width': width,
+                       'height': height}]
+            yaml.dump(config, yaml_file, default_flow_style=False)
+        cmd = 'img_checker'
+        output = run(cmd, stdout=Capture(), stderr=Capture())
+        if (output.returncode):
+            lines = output.stdout.text.split('\n')[1:-2]
+            for line in lines:
+                if '.png' in line:
+                    fileName = line[10:line.index('.png')+4]
+                if '.jpg' in line:
+                    fileName = line[10:line.index('.jpg')+4]
+                yield Result.from_values(origin=self,
+                                         message=line,
+                                         file=fileName,
+                                         severity=RESULT_SEVERITY.NORMAL)
+
+        os.remove('img_config.yml')

tests/general/ImageDimensionBearTest.py

@@ -0,0 +1,68 @@
+import unittest
+from queue import Queue
+import shutil
+
+from bears.general.ImageDimensionBear import ImageDimensionBear
+from coalib.settings.Section import Section
+
+
+class ImageDimensionBearTest(unittest.TestCase):
+    """
+    Runs unittests for ImageDimensionBear
+    """
+
+    def setUp(self):
+        self.section = Section('')
+        self.queue = Queue()
+        self.file_dict = {}
+        self.idb = ImageDimensionBear(None, self.section, self.queue)
+
+    def test_check_prerequisites(self):
+        _shutil_which = shutil.which
+        try:
+            shutil.which = lambda *args, **kwargs: None
+            self.assertEqual(ImageDimensionBear.check_prerequisites(),
+                             'img_checker is not installed.')
+
+            shutil.which = lambda *args, **kwargs: 'path/to/git'
+            self.assertTrue(ImageDimensionBear.check_prerequisites())
+        finally:
+            shutil.which = _shutil_which    
+
+    def test_run_with_png(self):
+        message = "message='The image ./test-img/img.png is larger"
+        message += " than 240px x 240px [w x h]'"
+        self.assertIn(message,
+                      str(list(self.idb.run(
+                               image_file='./test-img/*.png',
+                               width=240,
+                               height=240))))
+
+    def test_run_with_jpg(self):
+        self.assertEqual('[]',
+                         str(list(self.idb.run(
+                                  image_file='./test-img/*.jpg',
+                                  width=240,
+                                  height=240))))
+
+    def test_run_with_jpg_fail(self):
+        message = "message='The image ./test-img/images.jpg is larger"
+        message += " than 50px x 50px [w x h]'"
+        self.assertIn(message,
+                      str(list(self.idb.run(
+                               image_file='./test-img/*.jpg',
+                               width=50,
+                               height=50))))
+
+    def test_run_with_both(self):
+        message_png = "message='The image ./test-img/img.png is larger"
+        message_png += " than 50px x 50px [w x h]'"
+        message_jpg = "message='The image ./test-img/images.jpg is larger"
+        message_jpg += " than 50px x 50px [w x h]'"
+        output = str(list(self.idb.run(image_file='./test-img/*.*',
+                                       width=50,
+                                       height=50)))
+        self.assertIn(message_png,
+                      output)
+        self.assertIn(message_jpg,
+                      output)