Description of problem:
Familiarizing myself with woffTools and on first use I hit this bug.

The font is from this site:
http://www.sil.org/resources/software_fonts/andika
You can find it in an archive here: http://scripts.sil.org/cms/scripts/render_download.php?format=file&media_id=Andika-1.004-web.zip&filename=Andika-1.004-web.zip

$ woff-validate Andika-R.woff 
Testing: Andika-R.woff...
Traceback (most recent call last):
...
File "/usr/lib64/python2.7/site-packages/FontTools/sstruct.py", line 74, in pack
    data = apply(struct.pack, (formatstring,) + tuple(elements))
struct.error: integer out of range for 'L' format code

Version-Release number of selected component:
woffTools-0.1-0.7.684svn.fc20

Additional info:
reporter:       libreport-2.2.2
cmdline:        /usr/bin/python /usr/bin/woff-validate Andika-R.woff
dso_list:       fonttools-2.4-2.fc20.x86_64
executable:     /usr/bin/woff-validate
kernel:         3.14.4-200.fc20.x86_64
runlevel:       N 5
type:           Python
uid:            1000

Truncated backtrace:
sstruct.py:74:pack:error: integer out of range for 'L' format code

Traceback (most recent call last):
  File "/usr/bin/woff-validate", line 5, in <module>
    validate.main()
  File "/usr/lib/python2.7/site-packages/woffTools/tools/validate.py", line 1511, in main
    validateFont(fontPath, options)
  File "/usr/lib/python2.7/site-packages/woffTools/tools/validate.py", line 1450, in validateFont
    shouldStop = func(data, reporter)
  File "/usr/lib/python2.7/site-packages/woffTools/tools/validate.py", line 441, in testHeadCheckSumAdjustment
    newChecksum = calcHeadCheckSum(data)
  File "/usr/lib/python2.7/site-packages/woffTools/tools/validate.py", line 1383, in calcHeadCheckSum
    directory += sfntEntry.toString()
  File "/usr/lib64/python2.7/site-packages/FontTools/fontTools/ttLib/sfnt.py", line 227, in toString
    return sstruct.pack(sfntDirectoryEntryFormat, self)
  File "/usr/lib64/python2.7/site-packages/FontTools/sstruct.py", line 74, in pack
    data = apply(struct.pack, (formatstring,) + tuple(elements))
error: integer out of range for 'L' format code

Local variables in innermost frame:
elements: ['GDEF', -966601972, 1660, 2452]
name: 'length'
format: '\n\t\t> # big endian\n\t\ttag:            4s\n\t\tcheckSum:       L\n\t\toffset:         L\n\t\tlength:         L\n'
object: {'checkSum': -966601972, 'length': 2452, 'tag': 'GDEF', 'offset': 1660}
fixes: {}
formatstring: '>4sLLL'
value: 2452
names: ['tag', 'checkSum', 'offset', 'length']