refactor: move xmodule folder to root

- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
    - More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore

xmodule/tests/test_import_static.py

@@ -0,0 +1,56 @@
+"""
+Tests that check that we ignore the appropriate files when importing courses.
+"""
+
+
+import unittest
+from unittest.mock import Mock
+
+from opaque_keys.edx.locator import CourseLocator
+
+from xmodule.modulestore.tests.utils import (
+    DOT_FILES_DICT,
+    TILDA_FILES_DICT,
+    add_temp_files_from_dict,
+    remove_temp_files_from_list
+)
+from xmodule.modulestore.xml_importer import StaticContentImporter
+from xmodule.tests import DATA_DIR
+
+
+class IgnoredFilesTestCase(unittest.TestCase):
+    """
+    Tests for ignored files
+    """
+    course_dir = DATA_DIR / "course_ignore"
+    dict_list = [DOT_FILES_DICT, TILDA_FILES_DICT]
+
+    def setUp(self):
+        super().setUp()
+        for dictionary in self.dict_list:
+            self.addCleanup(remove_temp_files_from_list, list(dictionary.keys()), self.course_dir / "static")
+            add_temp_files_from_dict(dictionary, self.course_dir / "static")
+
+    def test_sample_static_files(self):
+        """
+        Test for to ensure Mac OS metadata files (filename starts with "._") as well
+        as files ending with "~" get ignored, while files starting with "." are not.
+        """
+        course_id = CourseLocator("edX", "course_ignore", "2014_Fall")
+        content_store = Mock()
+        content_store.generate_thumbnail.return_value = ("content", "location")
+        static_content_importer = StaticContentImporter(
+            static_content_store=content_store,
+            course_data_path=self.course_dir,
+            target_id=course_id
+        )
+        static_content_importer.import_static_content_directory()
+        saved_static_content = [call[0][0] for call in content_store.save.call_args_list]
+        name_val = {sc.name: sc.data for sc in saved_static_content}
+        assert 'example.txt' in name_val
+        assert '.example.txt' in name_val
+        assert b'GREEN' in name_val['example.txt']
+        assert b'BLUE' in name_val['.example.txt']
+        assert '._example.txt' not in name_val
+        assert '.DS_Store' not in name_val
+        assert 'example.txt~' not in name_val