tox failures- sqlalchemy cannot connect to mysql database

[megan]

[EXTENDED SUMMARY]: When running tox with the environment py*-func-mysql, sqlalchemy fails to connect to the internal MySQL server.

[ERROR MESSAGE]: sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 2] No such file or directory)")

[SUSPECTED CAUSE]: according to my quick precursory Google, it appears as though this error occurs when there is no MySQL server currently listening on port 3306.

[EXAMPLE TRACEBACK]:
Traceback (most recent call last):
  File "/opt/stack/refstack/refstack/tests/api/test_vendors.py", line 38, in setUp
    super(TestVendorsEndpoint, self).setUp()
  File "/opt/stack/refstack/refstack/tests/api/__init__.py", line 66, in setUp
    self.drop_all_tables_and_constraints()
  File "/opt/stack/refstack/refstack/tests/api/__init__.py", line 78, in drop_all_tables_and_constraints
    conn = engine.connect()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 2091, in connect
    return self._connection_cls(self, **kwargs)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 90, in __init__
    if connection is not None else engine.raw_connection()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 2177, in raw_connection
    self.pool.unique_connection, _connection)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 2151, in _wrap_pool_connect
    e, dialect, self)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 1465, in _handle_dbapi_exception_noconnection
    exc_info
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/util/compat.py", line 186, in reraise
    raise value.with_traceback(tb)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/base.py", line 2147, in _wrap_pool_connect
    return fn()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 328, in unique_connection
    return _ConnectionFairy._checkout(self)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 766, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 516, in checkout
    rec = pool._do_get()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 1138, in _do_get
    self._dec_overflow()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
    raise value
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 1135, in _do_get
    return self._create_connection()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 333, in _create_connection
    return _ConnectionRecord(self)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 461, in __init__
    self.__connect(first_connect_check=True)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/pool.py", line 651, in __connect
    connection = pool._invoke_creator(self)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/strategies.py", line 105, in connect
    return dialect.connect(*cargs, **cparams)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/sqlalchemy/engine/default.py", line 393, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/pymysql/__init__.py", line 90, in Connect
    return Connection(*args, **kwargs)
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/pymysql/connections.py", line 706, in __init__
    self.connect()
  File "/opt/stack/refstack/.tox/py35-func-mysql/lib/python3.5/site-packages/pymysql/connections.py", line 963, in connect
    raise exc
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 2] No such file or directory)")

[FULL TRACEBACK]:
can be found at https://beta.etherpad.org/p/refstack_mysql_bug_traceback
(or by just running tox with py27-func-mysql)

[Martin Kopec (mkopec)]

The tox environment mentioned above got moved to [functional] by:
https://opendev.org/osf/refstack/commit/35b3a1da4f0c1d59718517f787f40d19111c4c3e

It's passing now, so the bug got probably fixed over the time.