pub list fails on windows

[DartBot]

<img src="https://avatars.githubusercontent.com/u/5479?v=3" align="left" width="96" height="96"hspace="10"> Issue by sethladd
Originally opened as dart-lang/sdk#3383

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$ pub list
NoSuchMethodException : method not found: 'listDir'
Receiver: Instance of 'SystemCache'
Arguments: [null]
Unhandled exception:
NullPointerException : method: 'handleException'
Receiver: null
Arguments: [Closure: <T>(Dynamic) => Dynamic]
 0. Function: 'Object.noSuchMethod' url: 'bootstrap' line:473 col:137
 1. Function: 'FutureImpl.function' url: 'bootstrap_impl' line:565 col:350
 2. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:556 col:
3
 3. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:559 col:
22
 4. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:571 col:46
 5. Function: 'FutureImpl.function' url: 'bootstrap_impl' line:563 col:114
 6. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:556 col:
3
 7. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:559 col:
22
 8. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:571 col:46
 9. Function: 'FutureImpl.function' url: 'bootstrap_impl' line:567 col:61
 10. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:556 col
:3
 11. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:559 col
:22
 12. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:571 col:46
 13. Function: 'FutureImpl.function' url: 'bootstrap_impl' line:563 col:114
 14. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:556 col
:3
 15. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:559 col
:22
 16. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:571 col:46
 17. Function: 'FutureImpl.function' url: 'bootstrap_impl' line:563 col:114
 18. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:556 col
:3
 19. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:559 col
:22
 20. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:571 col:46
 21. Function: '_File@14117cc4.function' url: 'dart:io' line:224 col:48
 22. Function: '_BaseDataInputStream@14117cc4.issueCloseCallback' url: 'dart:io'
 line:866 col:125
 23. Function: '_Timer@14117cc4._handleTimeout@14117cc4' url: 'dart:io' line:116
4 col:66
 24. Function: '_Timer@14117cc4._handleTimeout@14117cc4' url: 'dart:io' line:116
4 col:182
 25. Function: '_Timer@14117cc4.function' url: 'dart:io' line:1164 col:341
 26. Function: '_ReceivePortImpl@6be832b._handleMessage@6be832b' url: 'dart:isol
ate' line:19 col:46

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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Added Duplicate label.
Marked as being merged into #41.