I am not sure if simply ignoring the non-valid character is the best way to go. Feels like silencing errors.

b64decode does accept the 'validate' flag - defaulted to False - that will halt the execution and throw an error.

What might be a good idea is to implement an 'errors' argument that accepts 'ignore' as a value, like we do for bytes.decode (https://docs.python.org/3/library/stdtypes.html#bytes.decode)