Convert two strings to bytestrings

[sldouglas-nist]

The patch converts two strings to bytes in get_file_info.py. The regular expression, reg in ascii_strings of get_file_info.py is looking through buf, which was previously annotated as bytes, meaning that reg needs to be bytes. Note the following example with inlined comments.

t substitutes for reg, exp for ascii_re, and test for buf

    # String buffer and string regex
    >>> import re
    >>> t = "t"
    >>> test = "test"
    >>> exp = re.compile(t)
    >>> for match in exp.finditer(test):
    ...     print(match)
    ...
    <re.Match object; span=(0, 1), match='t'>
    <re.Match object; span=(3, 4), match='t'>

    # Current code state
    >>> test = b"test"
    >>> for match in reg.finditer(test):
    ...     print(match)
    ...
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    TypeError: cannot use a string pattern on a bytes-like object

    # Modified code state
    >>> test = b"test"
    >>> t = b"t"
    >>> exp = re.compile(t)
    >>> for match in exp.finditer(test):
    ...     print(match)
    ...
    <re.Match object; span=(0, 1), match=b't'>
    <re.Match object; span=(3, 4), match=b't'>

The patch is written to pass mypy static type review when tested with the following:

    mypy list_mft.py MFTINDX.py

References:

• https://docs.python.org/3/library/re.html#re.finditer

[williballenthin]

looks great, thank you!

[sldouglas-nist]

This PR's branch is caught up and ready for merge when possible.