Fix handling of four byte utf8 manifests

- Adds the charset: utf-8 to all the manifest responses
- Makes sure we connect to MySQL in utf8mb4 mode, to ensure we can properly read and write 4-byte utf8 strings
- Adds tests for all of the above

test/fixtures.py

@@ -83,6 +83,7 @@ def _init_db_path_sqlite(tmpdir_factory):
   initialize_database()
 
   db.obj.execute_sql('PRAGMA foreign_keys = ON;')
+  db.obj.execute_sql('PRAGMA encoding="UTF-8";')
 
   populate_database()
   close_db_filter(None)
@@ -157,7 +158,9 @@ def initialized_db(appconfig):
   if not under_test_real_database:
     # Make absolutely sure foreign key constraints are on.
     db.obj.execute_sql('PRAGMA foreign_keys = ON;')
+    db.obj.execute_sql('PRAGMA encoding="UTF-8";')
     assert db.obj.execute_sql('PRAGMA foreign_keys;').fetchone()[0] == 1
+    assert db.obj.execute_sql('PRAGMA encoding;').fetchone()[0] == 'UTF-8'
 
   # If under a test *real* database, setup a savepoint.
   if under_test_real_database: