Non numeric STNNBR causes ValueError in get_datafile_filename for ctd writer(s)

[DocOtak]

Original report by abarna (Bitbucket: abarna, GitHub: abarna).

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The input file was the ctd exchange file from:
http://cchdo.ucsd.edu/cruise/49NZ20121128

A lovely traceback:

#!python

  File "/usr/local/cchdo/hydro-vm/src/libcchdo/scripts.py", line 2827, in main
    hydro_parser.exit(args.main(args))
  File "/usr/local/cchdo/hydro-vm/src/libcchdo/scripts.py", line 287, in any_to_type
    format.write(file, out_file)
  File "/usr/local/cchdo/hydro-vm/src/libcchdo/formats/ctd/zip/exchange.py", line 67, in write
    Zip.write(self, handle, ctdex, ctdex.get_datafile_filename)
  File "/usr/local/cchdo/hydro-vm/src/libcchdo/formats/zip.py", line 197, in write
    filename = get_filename(dfile)
  File "/usr/local/cchdo/hydro-vm/src/libcchdo/formats/ctd/exchange.py", line 59, in get_datafile_filename
    station = '%05d' % int(station)
ValueError: invalid literal for int() with base 10: 'C04'