Seems like it does not work anymore with keys without "umlaut"

When inserting titles without "umlaut" in the key it does not work anymore:

SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Body>
    <m:updateResponse xmlns:m="http://www.zotero.org/namespaces/SOAP">
      <output xmlns="http://purl.org/net/xbiblio/csl">!:!:0:{"sort"::true,"citationItems"::[{"itemID"::7163}]}:schwerdtfeger_1997</output>
    </m:updateResponse>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
DEBUG:root:['!', '!', '0', {u'sort': True, u'citationItems': [{u'itemID': 7163}]}, 'schwerdtfeger_1997']
DEBUG:root:{u'sort': True, u'citationItems': [{u'itemID': 7163}]}
Traceback (most recent call last):
  File "/home/chbeer/.gnome2/gedit/plugins/Zotero/zotero_interface.py", line 274, in add_citation
    cite_key = process_cite_key(cite_key)
  File "/home/chbeer/.gnome2/gedit/plugins/Zotero/zotero_interface.py", line 320, in process_cite_key
    key = unicodedata.normalize('NFKD', key).encode('ascii', 'ignore')
TypeError: normalize() argument 2 must be unicode, not str
DEBUG:root:['X']
DEBUG:root:Update parameters: [u'3XTOz7RH', 'false', 'updated', '!', '0', 'X']
DEBUG:root:<ns0:Envelope xmlns:ns0="http://schemas.xmlsoap.org/soap/envelope/"><ns0:Header /><ns0:Body><ns1:update xmlns:ns1="http://www.zotero.org/namespaces/SOAP"><input ns2:type="xsd:string" xmlns:ns2="http://www.w3.org/1999/XMLSchema-instance">3XTOz7RH:false:updated:!:0:X</input></ns1:update></ns0:Body></ns0:Envelope>
DEBUG:root:Response Status: 200
DEBUG:root:<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Body>
    <m:updateResponse xmlns:m="http://www.zotero.org/namespaces/SOAP">
      <output xmlns="http://purl.org/net/xbiblio/csl">!:!:0:{"sort"::true,"citationItems"::[{"itemID"::13815}]}:pekrun_elliot_maier_2006</output>
    </m:updateResponse>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
DEBUG:root:['!', '!', '0', {u'sort': True, u'citationItems': [{u'itemID': 13815}]}, 'pekrun_elliot_maier_2006']
DEBUG:root:{u'sort': True, u'citationItems': [{u'itemID': 13815}]}
Traceback (most recent call last):
  File "/home/chbeer/.gnome2/gedit/plugins/Zotero/zotero_interface.py", line 274, in add_citation
    cite_key = process_cite_key(cite_key)
  File "/home/chbeer/.gnome2/gedit/plugins/Zotero/zotero_interface.py", line 320, in process_cite_key
    key = unicodedata.normalize('NFKD', key).encode('ascii', 'ignore')
TypeError: normalize() argument 2 must be unicode, not str

with "Umlaut":
DEBUG:root:Response Status: 200
DEBUG:root:<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Body>
    <m:updateResponse xmlns:m="http://www.zotero.org/namespaces/SOAP">
      <output xmlns="http://purl.org/net/xbiblio/csl">!:!:0:{"sort"::true,"citationItems"::[{"itemID"::5052}]}:götz_pekrun_hall_haag_2006</output>
    </m:updateResponse>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
DEBUG:root:[u'!', u'!', u'0', {u'sort': True, u'citationItems': [{u'itemID': 5052}]}, u'g\xf6tz_pekrun_hall_haag_2006']
DEBUG:root:{u'sort': True, u'citationItems': [{u'itemID': 5052}]}