Strange "Badarg error in HTTP request" when submitting request object

[Marcus]

Hi,

I’m a pleased user working with couchdb 1.6.1 on OSX. Today I came across 
problems whose cause I don't know.
I’m using CouchDB-Python/0.10 to write on couchdb. When I submit this 
JSON-Object

{'docs': [{'from': u'+123456789101112', 'text': u'\ufffc', '_attachments': 
{u'Research Design_2. entwurf.pages': {'data': ‘here are 500kb als 
base64-encoded data', 'content_type': None}}, 'rowid': 46231, 'date': 
'2014-11-08T15:04:48', '_id': u'55F950E8-577F-45FB-AE5D-BC552C98F883', 'id': 
u'55F950E8-577F-45FB-AE5D-BC552C98F883'}]}

I got a 500-Error Message in response. The couchdb-log contains following items

[Sat, 06 Dec 2014 13:44:24 GMT] [error] [<0.2781.0>] Badarg error in HTTP 
request
[Sat, 06 Dec 2014 13:44:24 GMT] [info] [<0.2781.0>] Stacktrace: [{re,run,
                                     [null,
                                      ["^\\s*",
                                       [<<"text/">>,<<".*">>],
                                       "(?:\\s*;.*?)?\\s*",36],
                                      [caseless]],
                                     []},
                                 {couch_db,'-compressible_att_type/1-fun-0-',
                                     2,
                                     [{file,"couch_db.erl"},{line,972}]},
                                 {lists,any,2,
                                     [{file,"lists.erl"},{line,1223}]},
                                 {couch_db,with_stream,3,
                                     [{file,"couch_db.erl"},{line,991}]},
                                 {couch_db,'-doc_flush_atts/2-lc$^0/1-0-',2,
                                     [{file,"couch_db.erl"},{line,908}]},
                                 {couch_db,doc_flush_atts,2,
                                     [{file,"couch_db.erl"},{line,908}]},
                                 {couch_db,'-update_docs/4-lc$^7/1-7-',2,
                                     [{file,"couch_db.erl"},{line,777}]},
                                 {couch_db,'-update_docs/4-lc$^6/1-6-',2,
                                     [{file,"couch_db.erl"},{line,776}]}]
[Sat, 06 Dec 2014 13:44:24 GMT] [info] [<0.2781.0>] 127.0.0.1 - - POST 
/my-nice-table/_bulk_docs 500
[Sat, 06 Dec 2014 13:44:24 GMT] [error] [<0.2781.0>] httpd 500 error response:
 {"error":"unknown_error","reason":"badarg”}

Other JSOM-objects without an attachment can be successfully submitted to the 
tabel.

Does anyone have an idea what’s going wrong?

Best Regards

Marcus