Incoming API test fails with "TypeError: Incorrect padding"

From: https://0xacab.org/drebs/soledad/-/jobs/23154

=================================== FAILURES ===================================
 IncomingOnCouchServerTestCase.test_put_incoming_creates_a_blob_using_filesystem 

result = 1
g = <generator object test_put_incoming_creates_a_blob_using_filesystem at 0x7efdcdc2fd70>
deferred = <Deferred at 0x7efdce991368 current result: None>

    def _inlineCallbacks(result, g, deferred):
        """
        See L{inlineCallbacks}.
        """
        # This function is complicated by the need to prevent unbounded recursion
        # arising from repeatedly yielding immediately ready deferreds.  This while
        # loop and the waiting variable solve that by manually unfolding the
        # recursion.
    
        waiting = [True, # waiting for result?
                   None] # result
    
        while 1:
            try:
                # Send the last result back as the result of the yield expression.
                isFailure = isinstance(result, failure.Failure)
                if isFailure:
                    result = result.throwExceptionIntoGenerator(g)
                else:
>                   result = g.send(result)

.tox/py27/local/lib/python2.7/site-packages/twisted/internet/defer.py:1386: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
tests/server/test_incoming_server.py:92: in test_put_incoming_creates_a_blob_using_filesystem
    expected_preamble = decode_preamble(expected_preamble, True)
src/leap/soledad/common/blobs/preamble.py:87: in decode_preamble
    encoded_preamble = base64.b64decode(encoded_preamble)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

s = 'EzcCAwAAAAAym-RZAAAAAAAAAAAAAAAAAAAAAAAAAAAgOTkyZDNiNzdjNzIwNDY0Nzg3MjE3YWZmYWEwOTBlMGMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIAAAAAAAAA'
altchars = None

    def b64decode(s, altchars=None):
        """Decode a Base64 encoded string.
    
        s is the string to decode.  Optional altchars must be a string of at least
        length 2 (additional characters are ignored) which specifies the
        alternative alphabet used instead of the '+' and '/' characters.
    
        The decoded string is returned.  A TypeError is raised if s were
        incorrectly padded or if there are non-alphabet characters present in the
        string.
        """
        if altchars is not None:
            s = _translate(s, {altchars[0]: '+', altchars[1]: '/'})
        try:
            return binascii.a2b_base64(s)
        except binascii.Error, msg:
            # Transform this exception for consistency
>           raise TypeError(msg)
E           TypeError: Incorrect padding

/usr/lib/python2.7/base64.py:76: TypeError
!!!!!!!!!!!!!!!!!!!! Interrupted: stopping after 1 failures !!!!!!!!!!!!!!!!!!!!