EnvironmentError: Font generation failed error while patching AnkaCoder font

[AnwarShah]

While trying to patch AnkaCoder font, I faced this error

The glyph named Delta is mapped to U+0394.
But its name indicates it should be mapped to U+2206.
The glyph named Omega is mapped to U+03A9.
But its name indicates it should be mapped to U+2126.
The glyph named mu is mapped to U+03BC.
But its name indicates it should be mapped to U+00B5.
Save Failed
Traceback (most recent call last):
  File "./powerline-fontpatcher", line 146, in <module>
    raise SystemExit(main(sys.argv[1:]))
  File "./powerline-fontpatcher", line 143, in main
    return patch_fonts(args.source_font, args.target_fonts, args.rename_font)
  File "./powerline-fontpatcher", line 135, in patch_fonts
    patch_one_font(source_font, target_font, rename_font)
  File "./powerline-fontpatcher", line 127, in patch_one_font
    target_font.generate('{0}{1}'.format(target_font.fullname, extension))
EnvironmentError: Font generation failed

Before it throws this error
TypeError: No such glyph but I used this patch #13 to overcome it.