Suddenly error with decoding unicode not supported

[Behinder]

Code worked fine for 2 years now it is not:

Traceback (most recent call last):
  File "EPFImporter.py", line 454, in <module>
    main()
  File "EPFImporter.py", line 437, in main
    fieldDelim=fieldSep)
  File "EPFImporter.py", line 222, in doImport
    ing.ingest(skipKeyViolators=skipKeyViolators)
  File "/Users/sebastian/Documents/test2/EPFIngester.py", line 111, in ingest
    self.ingestIncremental(skipKeyViolators=skipKeyViolators)
  File "/Users/sebastian/Documents/test2/EPFIngester.py", line 206, in ingestIncremental
    skipKeyViolators=skipKeyViolators)
  File "/Users/sebastian/Documents/test2/EPFIngester.py", line 375, in _populateTable
    colVals = unicode(", ".join(stringList), 'utf-8')
TypeError: decoding Unicode is not supported