Setting host maps in omshell fails

The task is called but no host map is added in the leases file. Debugging in the maas shell shows:

>>> NodeGroup.objects.all()[0].dhcp_key
u'YXY5pr+No/8NZeodSd27wWbI8N6kIjMF/nrnFIlPwVLuByJKkQcBRtfDrDLLG2U9/ND7/bIlJxEGTUnyipffHQ=='
>>> omshell=Omshell('127.0.0.1','YXY5pr+No/8NZeodSd27wWbI8N6kIjMF/nrnFIlPwVLuByJKkQcBRtfDrDLLG2U9/ND7/bIlJxEGTUnyipffHQ==')
>>> omshell.create('10.0.0.100','e4:11:5b:13:7b:36')
<STDIN> line 1: partial base64 value left over: 2.
key omapi_key YXY5pr+No/
                     ^