Fix exceptions on windows disks/partitions

[dbwiddis]

Fixes #238

[coveralls]

Coverage decreased (-0.2%) to 91.611% when pulling 3b542fe on dbwiddis:master into ab1ebd2 on dblock:master.

[codecov-io]

Current coverage is 85.79% (diff: 100%)

Merging #239 into master will increase coverage by 0.03%

@@             master       #239   diff @@
==========================================
  Files            23         23          
  Lines           892        894     +2   
  Methods           0          0          
  Messages          0          0          
  Branches        129        130     +1   
==========================================
+ Hits            765        767     +2   
  Misses           60         60          
  Partials         67         67          

Powered by Codecov. Last update 2a4928c...82b9dfe

[coveralls]

Coverage increased (+0.02%) to 91.834% when pulling 8301913 on dbwiddis:master into ab1ebd2 on dblock:master.

[coveralls]

Coverage increased (+0.02%) to 91.834% when pulling 82b9dfe on dbwiddis:master into 2a4928c on dblock:master.