`time.strftime(arg)` fails when arg is not valid format string

jopemachine

Expected Result

In cpython, when arg is not a valid format string, strftime returns arg itself.

>>> import time
>>> time.strftime("%Y")
'2022'
>>> time.strftime("%4Y")
'4Y'

Actual Result

~~In RustPython, strftime raise panic when arg is not a valid format string~~

>>>>> import time
>>>>> time.strftime("%Y")
'2022'
>>>>> time.strftime("%4Y")
thread 'main' panicked at 'a Display implementation returned an error unexpectedly: Error', /rustc/4b91a6ea7258a947e59c6522cd5898e7c0a6a88f/library/alloc/src/string.rs:2490:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace