Thanks for the patch Alex. Some quick review comments:

* We need to skip SqliteOnConflictTests if the installed sqlite3 doesn't support the feature

* There is no need to duplicate https://www.sqlite.org/lang_conflict.html in every test. You can add it to SqliteOnConflictTests docstring.

* Instead of ``try: <something> except sqlite.IntegrityError: <pass>`` we can make sure that sqlite.IntegrityError is raised by using assertRaises (like you did in CheckOnConflictFail.)

* The following pattern can be replaced with a list comprehension:

  +        returned_rows = []
  +        for row in self.cu:
  +            returned_rows.append(row)