not working on python3.7, potentially not compatible with many versions of python3

[sargense]

when writing to file, it requires a bytes like object
--> 177 self.mmap_buffer.write(item)
TypeError: a bytes-like object is required, not 'str'

--> 147 assert type(item) is str, "items put into ring buffer must be strings"
AssertionError: items put into ring buffer must be strings

[sargense]

Seems to work fine with just changing the assert to bytes.