DeleteFileAction: New action for DuplicateFileBear

Added a new action DeleteFileAction for DuplicateFileBear. Two instances
of this action are added corresponding to the files. On applying it will
delete one the file.

bears/general/actions/DeleteFileAction.py

@@ -0,0 +1,26 @@
+import os
+from coalib.results.result_actions.ResultAction import ResultAction
+
+
+class DeleteFileAction(ResultAction):
+    """
+    Deletes a file
+    """
+
+    SUCCESS_MESSAGE = 'File deleted successfully.'
+
+    def __init__(self, filename):
+        self.filename = filename
+        self.description = ('Delete {} [Note: This will '
+                            'delete the file permanently]').format(filename)
+
+    @staticmethod
+    def is_applicable(result,
+                      original_file_dict,
+                      file_diff_dict,
+                      applied_actions=()):
+        return 'DeleteFileAction' not in applied_actions
+
+    def apply(self, result, original_file_dict, file_diff_dict):
+        os.remove(self.filename)
+        return file_diff_dict

tests/general/actions/DeleteFileActionTest.py

@@ -0,0 +1,33 @@
+import os
+import unittest
+from unittest.mock import patch
+from coalib.results.Result import Result
+from bears.general.actions.DeleteFileAction import DeleteFileAction
+from coala_utils.ContextManagers import retrieve_stdout
+
+def get_path(file):
+    return os.path.join(
+        os.getcwd(), 'tests', 'general', 'duplicate_test_files', file)
+
+class DeleteFileActionTest(unittest.TestCase):
+
+    def setUp(self):
+        self.file1 = 'complexFirst.txt'
+        self.file2 = 'complexSecond.txt'
+        self.result = Result('origin', 'message')
+        self.uut1 = DeleteFileAction(self.file1)
+        self.uut2 = DeleteFileAction(self.file2)
+
+    def test_is_applicable(self):
+        self.assertTrue(self.uut1.is_applicable(self.result, {}, {}))
+        self.assertFalse(self.uut1.is_applicable(
+            self.result, {}, {}, applied_actions=('DeleteFileAction')))
+
+    def test_apply(self):
+        with retrieve_stdout() as stdout:
+            patcher = ('bears.general.actions.DeleteFileAction.'
+                       'os.remove')
+            with patch(patcher):
+                ret = self.uut1.apply(self.result, {}, {'file': 'diff'})
+                self.assertEqual(ret, {'file': 'diff'})
+                self.assertEqual(stdout.getvalue(), '')