Issue exporting schematic to PDF

[guyzmo]

Schematic -> PDF

cf issue #5

I wonder if this is even possible but since the PNG export worked like a charm I suppose that I shouldn't get the following error:

$ pea export schematic.sch pdf schematic.pdf
Traceback (most recent call last):
  File "/usr/local/bin/pea", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.5/site-packages/eagle_automation/pea.py", line 86, in main
    return eagle_automation.export.export_main(verbose=args['--verbose'])
  File "/usr/local/lib/python3.5/site-packages/eagle_automation/export.py", line 468, in export_main
    export_class(verbose=verbose).export(args['<input>'], layers, out_paths)
  File "/usr/local/lib/python3.5/site-packages/eagle_automation/export.py", line 57, in export
    script = self.write_script(extension, layers, out_paths)
  File "/usr/local/lib/python3.5/site-packages/eagle_automation/export.py", line 284, in write_script
    raise BadExtension
TypeError: exceptions must derive from BaseException

There's a problem with the exceptions I'm using which leads to you not understanding what went wrong:

TypeError: exceptions must derive from BaseException

which originally is a BadExtension issue. So, I believe that error is because it's not finding the pdf handling code, and the mystery to solve is to understand why…