travis: fix erros

* set mysql password
* add mysql to services

.travis.yml

@@ -12,6 +12,9 @@ python:
 
 cache: pip
 
+services:
+  - mysql
+
 install:
   - pip install -U pip
   - pip install -U mock coverage pytest pytest-cov

tests/travis.cnf

@@ -7,5 +7,5 @@ host = 127.0.0.1
 port = 3306
 user = root
 database = mysqldb_test
-#password =
+password = travis
 default-character-set = utf8mb4