bug#32390:

[Carlos Pita]

Sorry, it's not the first condition that is failing but the second one:

           (not (member
                 (python-shell-comint-end-of-output-p
                  (ansi-color-filter-apply output))
                 '(nil 0))))

(ansi-color-filter-apply output) is removing the error message so that
only the next input prompt remains. The entire expression evaluates to
nil for error output, at least when:

 '(python-shell-interpreter "ipython")
 '(python-shell-interpreter-args "-i --simple-prompt")