Switch assemble_changelog to using text strings
Switch assemble_changelog to using text strings

Changelog contents should be UTF-8 text files. There's no need to be
binary-safe. So switch to using text strings in Python (str, not bytes). This
commit makes the following changes:
* Bytes literals (b'…') to string literals ('…').
* Subprocess output (which is all git information) is decoded as ascii.
* Inject text directly in exceptions rather than calling a decode method.

This is enough to make the script work as desired in a UTF-8 locale.

Signed-off-by: Gilles Peskine <f805f64266d288fc5467baa7be6cd0ff366f477b@arm.com>

NXPmicro/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls