Magic Folder on Windows: admin privileges needed to run tests on Windows 7+

[daira]

Running the drop-upload tests without admin privileges on Windows 7 gives these errors when run from a normal (non-admin) command prompt:

[ERROR]
Traceback (most recent call last):
  File "c:\tahoe\git\tahoe-magic\src\allmydata\test\test_drop_upload.py", line 247, in <lambda>
    d.addCallback(lambda ign: self._check_file(u"short", "test"))
  File "c:\tahoe\git\tahoe-magic\src\allmydata\test\test_drop_upload.py", line 298, in _check_file
    fileutil.flush_volume(path_u)
  File "c:\tahoe\git\tahoe-magic\src\allmydata\util\fileutil.py", line 599, in flush_volume
    raise WinError(get_last_error())
exceptions.WindowsError: [Error 6] The handle is invalid.

allmydata.test.test_drop_upload.MockTest.test_drop_upload
allmydata.test.test_drop_upload.RealTest.test_drop_upload

(probably also on Windows Vista, but no-one will ever make me care about Vista any more).

FlushFileBuffers on a drive is indeed ​documented to require admin privs:

To flush all open files on a volume, call FlushFileBuffers with a handle to the volume. The caller must have administrative privileges.

I'm not actually sure that flushing buffers is still necessary; for the time being I'll keep it in until the tests are fully debugged, and then try removing it.

[daira]

It probably also required admin privs on XP, but that was hidden because there was no need to elevate to get those privs from the account I was using.

[daira]

Notice the terrible error reporting -- pretty typical for Win32 APIs.

[daira]

Add magic-folder keyword to all drop-upload tickets.

[daira]

This is not a blocker for merging Magic Folder to trunk.

[daira]

However, the tests should be skipped if they can't be run for this reason. (I don't know whether the tests will end up needing flush_volume; if possible we should remove that.)

[warner]

Milestone renamed

[daira]

We removed the calls to flush_volume.