Reporting an issue from https://github.com/xonsh/xonsh/issues/3581; boils down to, ast.Call used to not define end_lineno in 3.8:

py -3.8 -c 'import ast; type(ast.Call().end_lineno)'                                                                                                                                                                 Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: 'Call' object has no attribute 'end_lineno'

However in 3.9 is defined with None:

py -3.9 -c 'import ast; type(ast.Call().end_lineno)'

This messes with some other operations in ast, namely https://github.com/python/cpython/blob/master/Lib/ast.py#L233