By default, shutil.rmtree raises an exception when deleting readonly
files on Windows.
Replace all shutil.rmtree with platform_utils.rmtree, which adds an
error handler to make files read-write when they can't be deleted.
Change-Id: I9cfea9a7b3703fb16a82cf69331540c2c179ed53
Replace all calls to os.symlink with platform_utils.symlink.
The Windows implementation calls into the CreateSymbolicLinkW Win32
API, as os.symlink is not supported.
Separate the Win32 API definitions into a separate module
platform_utils_win32 for clarity.
Change-Id: I0714c598664c2df93383734e609d948692c17ec5
Python on Windows does not support non blocking file operations.
To workaround this issue, we instead use Threads and a Queue to
simulate non-blocking calls. This is happens only when running
with the native Windows version of Python, meaning Linux and Cygwin
are not affected by this change.
Change-Id: I4ce23827b096c5138f67a85c721f58a12279bb6f
