Add quiet switch

As is, dbmigrator is a bit chatty. I will take advantage of this in
cnx-db/script/ci_test_migrations.sh to make non-CI invocation almost
completely silent, so migration failures stand out.

dbmigrator/cli.py

@@ -32,6 +32,7 @@ def main(argv=sys.argv[1:]):
     parser = argparse.ArgumentParser(description='DB Migrator')
 
     parser.add_argument('--verbose', '-v', action='store_true')
+    parser.add_argument('--quiet', '-q', action='store_true')
 
     parser.add_argument('--migrations-directory',
                         action='append',
@@ -97,6 +98,9 @@ def main(argv=sys.argv[1:]):
     if args.get('verbose'):
         logger.setLevel(logging.DEBUG)
 
+    if args.get('quiet'):
+        logger.setLevel(logging.ERROR)
+
     logger.debug('args: {}'.format(args))
     utils.set_settings(args)
 

dbmigrator/tests/test_cli.py

@@ -85,6 +85,13 @@ def test(self):
         logger.info.assert_called_with('Schema migrations initialized.')
 
 
+class QuietTestCase(BaseTestCase):
+    def test(self):
+        self.target(['-q', '--config', testing.test_config_path, 'init'])
+
+        logger.setLevel.assert_called_with(logging.ERROR)
+
+
 class ListTestCase(BaseTestCase):
     def test_no_migrations_directory(self):
         cmd = ['--db-connection-string', testing.db_connection_string]