Problem generating plist for font

[kekearif]

Hey, I'm tying to add my own custom font. However I am having issues using the included script to generate a plist. How do you generate the plist?

I tried to generate the plist first with the included font file (just for testing purposes) latinmodern-math.otf. I did the following steps:

• First convert to ttx using ttx latinmodern-math.otf in the terminal from the Python fonttools library.
• I then run the script included in the repo to try and generate a plist python math_table_to_plist.py latinmodern-math.ttx latinmodern-math.plist

However when I run the script I get the following error:

Traceback (most recent call last):
  File "math_table_to_plist.py", line 203, in <module>
    main()
  File "math_table_to_plist.py", line 200, in main
    process_font(font_file, plist_file)
  File "math_table_to_plist.py", line 11, in process_font
    font = TTFont(font_file)
  File "/Users/kekearif/Desktop/font/lib/python2.7/site-packages/fontTools/ttLib/ttFont.py", line 140, in __init__
    self.reader = SFNTReader(file, checkChecksums, fontNumber=fontNumber)
  File "/Users/kekearif/Desktop/font/lib/python2.7/site-packages/fontTools/ttLib/sfnt.py", line 81, in __init__
    raise TTLibError("Not a TrueType or OpenType font (bad sfntVersion)")
fontTools.ttLib.TTLibError: Not a TrueType or OpenType font (bad sfntVersion)

Any idea what I am doing wrong where and why I am getting this error?