Workaround Path/XML string too long on Windows OS

[Liam-Deacon]

Provides a workaround for #45 (and #52?) when attempting to input a long XML string into os.path.exists() function when on Windows OS.

For reference, the size of string must be ≥ 2^15 (or 32768) characters - at least on Windows 10 - to trigger the issue!

[coveralls]

Coverage increased (+0.3%) to 35.185% when pulling 6c4e502 on Lightslayer:master into cd441fd on stchris:master.

[stchris]

I want to address the "magic" aspect of detecting the input in #87