TypeError: compile() expected string without null bytes

[mw66]

/local/lib/python2.7/site-packages/macropy/core/import_hooks.py", line 43, in find_module
    tree = ast.parse(txt)
  File "/usr/lib/python2.7/ast.py", line 37, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
TypeError: compile() expected string without null bytes