time.strftime(arg) fails when arg is not valid format string #4157
Description
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