Fixed #27848 -- Prevented crash when attaching a .eml file to a message

[claudep]

Thanks Sébastien Ramage for the report.

[timgraham]

Is it worth a comment explaining the usage of force_text() as opposed to str() (the test seems to pass either way)?

[claudep]

Oh, sorry, I didn't check your comment before the commit :-(
Generally, force_text is a bit more resilient when we are not sure about character encodings of the source. Agreed that we might add some tests. However I didn't investigate about accepted encodings for .eml files.

[timgraham]

if isinstance(s, bytes):
    s = str(s, encoding, errors)
else:
    s = str(s)

It looks to me like force_text() (without encoding/errors args) behaves the same as str(), considering the the default values for encoding and errors is the same for force_text() and str(). Is this analysis correct? I'm just trying to understand a bit better.

[claudep]

Not really:

In [1]: from django.utils.encoding import force_text

In [2]: encoded = "café".encode()

In [3]: str(encoded)
Out[3]: "b'caf\\xc3\\xa9'"

In [4]: force_text(encoded)
Out[4]: 'café'

[timgraham]

Thanks, I didn't read https://docs.python.org/3/library/stdtypes.html#str closely enough.