Python unittests run multiple times

I have the problem, that some of my unittests run multiple times, but I can't figure out why.

Here's the code with the tests:

# -*- coding: utf-8 -*-
"""Tests for api.resource.decorators"""

import os
import errno
import unittest
import logging
from socket import gaierror, error as socketerror
from lockfile import LockFile
from logging import FileHandler, Formatter
from api.resource.decorators import handle_general_exceptions


class TestHandleGeneralExceptions(unittest.TestCase):
    _tmp_log_path = '/tmp/test_handle_general_exceptions_log'
    _tmp_lock_path = '/tmp/test_handle_general_exceptions_lock'
    _lock = None
    _logger = None

    def setUp(self):
        self._lock = self._get_lock()
        self._logger = self._get_logger()

    def tearDown(self):
        self._remove_lockfiles()

    def _remove_lockfiles(self):
        # TODO: solve without system call
        os.system('rm -f %s*' % self._tmp_lock_path)

    def _get_lock(self):
        return LockFile(self._tmp_lock_path)

    def _get_logger(self):
        logger = logging.getLogger('handle_general_exceptions')
        logger.propagate = False # Only use this Logger
        handler = FileHandler(self._tmp_log_path)
        formatter = Formatter('%(asctime)s [%(levelname)s] %(message)s',
                              datefmt='%Y-%m-%d %H:%M:%S')
        handler.setFormatter(formatter)
        logger.addHandler(handler)
        logger.setLevel('INFO')
        return logger

    def _raise_gaierror(self):
        self._lock.acquire(-1)
        raise gaierror(-2, 'Name or service not known')

    def _raise_connection_timed_out(self):
        self._lock.acquire(-1)
        raise socketerror(errno.ETIMEDOUT, 'Connection Timed Out')

    def _raise_connection_refused(self):
        self._lock.acquire(-1)
        raise socketerror(errno.ECONNREFUSED, 'Connection Refused')

    def _is_locked(self):
        return os.path.exists(self._tmp_lock_path + '.lock') == 1

    def test_not_locked_if_gaierror_occurred(self):
        self._raise_gaierror = handle_general_exceptions(
            self._lock, self._logger, self._raise_gaierror)
        self._logger.info('¯¯¯¯¯¯¯¯¯¯¯¯ _raise_gaierror() ¯¯¯¯¯¯¯¯¯¯¯¯')
        self._raise_gaierror()
        self._logger.info('____________ End _raise_gaierror() ____________')
        self.assertFalse(self._is_locked())

    def test_not_locked_if_connection_timed_out(self):
        self._raise_connection_timed_out = \
            handle_general_exceptions(self._lock, self._logger,
                self._raise_connection_timed_out)
        self._logger.info(
            '¯¯¯¯¯¯¯¯¯¯¯¯ _raise_connection_timed_out() ¯¯¯¯¯¯¯¯¯¯¯¯')
        self._raise_connection_timed_out()
        self._logger.info(
            '____________ End _raise_connection_timed_out() ____________')
        self.assertFalse(self._is_locked())

    def test_not_locked_if_connection_refused(self):
        self._raise_connection_refused = \
            handle_general_exceptions(self._lock, self._logger,
                self._raise_connection_refused)
        self._logger.info(
            '¯¯¯¯¯¯¯¯¯¯¯¯ _raise_connection_refused() ¯¯¯¯¯¯¯¯¯¯¯¯')
        self._raise_connection_refused()
        self._logger.info(
            '____________ End _raise_connection_refused() ____________')
        self.assertFalse(self._is_locked())

And the tests are executed via a script like this:

#!/bin/sh

python -m unittest discover api.tests -t .

Now the test test_not_locked_if_gaierror_occurred() is executed 3 times.

The test test_not_locked_if_connection_timed_out() is executed 2 times.

And the test test_not_locked_if_connection_refused() is executed once.