fix in pyinstaller spec

Author: spderosso

gl.spec

@@ -3,9 +3,11 @@ import os
 
 a = Analysis(['gl.py'],
              pathex=[os.getcwd()],
-             # https://github.com/pyinstaller/pyinstaller/issues/3198
-             # remove this when dropping support for Python < 3.7
-             hiddenimports=['_sysconfigdata'],
+             hiddenimports=[
+               # https://github.com/pyinstaller/pyinstaller/issues/3198
+               # remove this when dropping support for Python < 3.7
+               '_sysconfigdata',
+               '_cffi_backend'],
              hookspath=None,
              runtime_hooks=None)