In zoneinfo._tzpath, _validate_tzfile_path() depends on os.path.normpath(). I think the Windows implementation of normpath() in the ntpath module should be extended to normalize reserved names in the final path component in the same manner as WinAPI GetFullPathNameW(). 

Alternatively, an isreserved() function could be added to os.path. This would allow _validate_tzfile_path() to raise a more informative exception for a reserved name.

Reserved names:

GetFullPathNameW() strips trailing spaces and dots from the final path component. This applies to all path types. For example:

    >>> nt._getfullpathname('\\\\?\\UNC/server/share/spam. . .')
    '\\\\?\\UNC\\server\\share\\spam'

GetFullPathNameW() reserves DOS device names in the final component of a relative path or drive path -- but not in a UNC path or device path. The following case-insensitive names are reserved:

    * NUL
    * CON
    * CONIN$
    * CONOUT$
    * AUX
    * PRN
    * COM<1-9>
    * LPT<1-9>

A reserved device name begins with one of the above base names plus an optional suffix. The suffix is zero or more spaces followed optionally by a "." or ":" and zero or more characters. The normalized result is a "\\\\.\\" device path for the base device name. For example: 

    >>> nt._getfullpathname('C:/Temp/con . spam')
    '\\\\.\\con'
    >>> nt._getfullpathname('C:/Temp/con : spam')
    '\\\\.\\con'