Support Google Font dependencies

Allow downloading fonts from Google Font at install time.
Closes GitLab issue #595, thanks to Martin (@efelon) for the
report. Closes re-opened GitLab issue #343.
Remove included Lato font.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/dependencies/tests/test_classes.py

@@ -0,0 +1,53 @@
+from __future__ import print_function, unicode_literals
+
+from pathlib2 import Path
+import shutil
+
+from mayan.apps.common.tests import BaseTestCase
+from mayan.apps.storage.utils import mkdtemp
+
+from ..classes import Dependency, Provider
+
+
+class TestProvider(Provider):
+    """Test provider"""
+
+
+class TestDependency(Dependency):
+    provider_class = TestProvider
+
+
+class DependencyClassTestCase(BaseTestCase):
+    def test_file_patching(self):
+        test_replace_text = 'replaced_text'
+
+        temporary_directory = mkdtemp()
+        path_temporary_directory = Path(temporary_directory)
+        path_test_file = path_temporary_directory / 'test_file.css'
+
+        with open(path_test_file, mode='w') as file_object:
+            file_object.write(
+                '@import url("https://fonts.googleapis.com/css?family=Lato:400,700,400italic");'
+            )
+
+        dependency = TestDependency(name='test_dependency', module=__name__)
+        replace_list = [
+            {
+                'filename_pattern': '*',
+                'content_patterns': [
+                    {
+                        'search': '"https://fonts.googleapis.com/css?family=Lato:400,700,400italic"',
+                        'replace': test_replace_text,
+                    }
+                ]
+            }
+        ]
+
+        dependency.patch_files(path=temporary_directory, replace_list=replace_list)
+
+        with open(path_test_file, mode='r') as file_object:
+            final_text = file_object.read()
+
+        shutil.rmtree(temporary_directory, ignore_errors=True)
+
+        self.assertEqual(final_text, '@import url({});'.format(test_replace_text))