Issue generating metadata.json on debian without python module simplejson

[autious]

This is a minor issue, but these notes may help anyone that comes after me.

When running the script on a debian machine

Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 GNU/Linux

Using packaged python version 2.7.3

I get the following error:

Reading image resources
Packing 20 images to sprite-sheets
1.png 20 images was packed with pixel overhead of 24.19%
Traceback (most recent call last):
File "/usr/local/bin/art-packer", line 5, in
pkg_resources.run_script('artpacker==1.0.1', 'art-packer')
File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 499, in run_script
self.require(requires)[0].run_script(script_name, ns)
File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1235, in run_script
execfile(script_filename, namespace, namespace)
File "/usr/local/lib/python2.7/dist-packages/artpacker-1.0.1-py2.7.egg/EGG-INFO/scripts/art-packer", line 10, in
main()
File "/usr/local/lib/python2.7/dist-packages/artpacker-1.0.1-py2.7.egg/artpacker/cli.py", line 102, in main
verbose=options.verbose).generate()
File "/usr/local/lib/python2.7/dist-packages/artpacker-1.0.1-py2.7.egg/artpacker/artpacker.py", line 91, in generate
self.metadata_saver.save({'sheets': sprite_sheets, 'sprites': metadata})
File "/usr/local/lib/python2.7/dist-packages/artpacker-1.0.1-py2.7.egg/artpacker/metadata/json.py", line 14, in save
content = BANNER + json.dumps(metadata, indent=' ')
AttributeError: 'module' object has no attribute 'dumps'

Note the last line.

Installing the debian package python-simplejson turned out to be a quick way of fixing this issue for me.

From what i can gather from this post: http://stackoverflow.com/questions/11369734/python-json-module-has-no-attribute-dumps

The reason for the error might be the compounding circumstances of having a file named json.py and not having simplejson available thus falling back on the json module. This might result in that the json.py file gets loaded incorrectly due to its name.