nicknym: error uploading key

key uploading fails when tried in cdev.bitmask.net

2016-12-29T15:54:40+0100 [leap.bitmask.core.mail_services#error] Error while sending key!
2016-12-29T15:54:40+0100 [leap.bitmask.core.mail_services#error] Unable to format event {'log_namespace': 'leap.bitmask.core.mail_services', 'log_level': , 'log_logger': , 'log_time': 1483023280.882622, 'log_source': None, 'log_format': }: Log format must be unicode or bytes, not 
2016-12-29T15:54:40+0100 [twisted.internet.defer#critical] Unhandled error in Deferred:
2016-12-29T15:54:40+0100 [twisted.internet.defer#critical] 
	Traceback (most recent call last):
	  File "site-packages/twisted/internet/defer.py", line 457, in callback
	    
	  File "site-packages/twisted/internet/defer.py", line 565, in _startRunCallbacks
	    
	  File "site-packages/twisted/internet/defer.py", line 651, in _runCallbacks
	    
	  File "site-packages/twisted/internet/defer.py", line 1355, in gotResult
	    
	---  ---
	  File "site-packages/twisted/internet/defer.py", line 1299, in _inlineCallbacks
	    
	  File "leap/bitmask/keymanager/nicknym.py", line 92, in put_key
	    
	exceptions.Exception: {"error":"The server failed to process your request. We'll look into it (MultiJson::ParseError)."}

(from redmine: created on 2016-12-29)