Why does MachineError.__str__ use repr()?

[kopsha]

Hello,

I noticed that the MachineError class defines __str__ as

class MachineError(Exception):
    def __str__(self):
        return repr(self.value)

This means that when the value is a string, the result includes quotes. This behavior is a bit inconvenient when the exception message needs to be forwarded to a user-facing context (e.g., API error message), since the quotes are not semantically part of the message.

Was there a specific reason for using repr() here (e.g., debugging consistency, preserving non-string types), or could str(self.value) be more appropriate to make the message cleaner for string values?

Thank you for your time and for maintaining such a well-designed library!