Probably nodename nor servname provided, or not known needs to be added to list of allowed outputs of the test_error_message_reuse test.

log:

self = <test.test_error.TestErrorConversion object at 0x110663910>

    def test_error_message_reuse(self):
        """
        Test if the error message string is retained if the caught exception
        has more than one element in `args`.
        """
        # See ticket <a href="/~sschwarzer/ftputil/76" title="~sschwarzer/ftputil#76: Error message related to OS">#76</a>.
        with pytest.raises(ftputil.error.FTPOSError) as exc_info:
            # Format "host:port" doesn't work. The use here is intentional.
            host = ftputil.FTPHost("localhost:21", "", "")
        exc = exc_info.value
        # The error message may be different for different Python versions.
>       assert "No address associated with hostname" in str(
            exc
        ) or "Name or service not known" in str(exc)
E       AssertionError: assert ('No address associated with hostname' in '[Errno 8] nodename nor servname provided, or not known\nDebugging info: ftputil 4.0.0, Python 3.8.6 (darwin)' or 'Name or service not known' in '[Errno 8] nodename nor servname provided, or not known\nDebugging info: ftputil 4.0.0, Python 3.8.6 (darwin)')
E        +  where '[Errno 8] nodename nor servname provided, or not known\nDebugging info: ftputil 4.0.0, Python 3.8.6 (darwin)' = str(FTPOSError(8, 'nodename nor servname provided, or not known'))
E        +  and   '[Errno 8] nodename nor servname provided, or not known\nDebugging info: ftputil 4.0.0, Python 3.8.6 (darwin)' = str(FTPOSError(8, 'nodename nor servname provided, or not known'))

test/test_error.py:66: AssertionError