os: Remove(x) doesn't return an error that passes os.IsExist() on Windows

[akalin-keybase]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.7

What operating system and processor architecture are you using (go env)?

Windows

What did you do?

Example program:

https://play.golang.org/p/pd_mMUsR-c

What did you expect to see?

This should print "is exist = true" on Windows, too.

What did you see instead?

(Caveat: didn't run exactly this program, but a similar one.)

On Windows, an errno of 145 is returned, which corresponds to ERROR_DIR_NOT_EMPTY.

From https://golang.org/src/os/error_windows.go , it looks like this particular value isn't in isExist.

[bradfitz]

Thanks. Seems easy enough to fix.

/cc @alexbrainman

[gopherbot]

CL https://golang.org/cl/29753 mentions this issue.