testutils/patch.py: Add methods for applying and removing patches

tests/testutils/patch.py

+import subprocess
+
+
+def apply(file, patch):
+    try:
+        subprocess.check_output(['patch', file, patch])
+    except subprocess.CalledProcessError as e:
+        message = "Patch failed with exit code {}\n Output:\n {}".format(
+            e.returncode, e.output)
+        print(message)
+        raise
+
+
+def remove(file, patch):
+    try:
+        subprocess.check_output(['patch', '--reverse', file, patch])
+    except subprocess.CalledProcessError as e:
+        message = "patch --reverse failed with exit code {}\n Output:\n {}".format(
+            e.returncode, e.output)
+        print(message)
+        raise