Add compatibility with Windows

Windows places an exclusive lock on files opened for writing. So,
opening the temporary tarfile twice (once by `NamedTemporaryFile` and
another time by `tarfile.open(fd.name)` makes things croak with
`PermissionError: [Errno 13] Permission denied`.

Instead, let's reuse the file handle already opened by
`NamedTemporaryFile`.

CHANGES.md

@@ -9,6 +9,8 @@
 - Tests: Run test harness on GHA
 - Tests: Add Windows to test matrix on CI/GHA
 - Tests: Fix tests on Windows
+- Add compatibility with Windows regarding exclusive write-lock
+  at `NamedTemporaryFile` vs. `tarfile.open`
 
 
 ## 0.3.0 (2021-07-01)

wacklig.py

@@ -77,9 +77,10 @@ def upload_files(token, server, ci_info, files):
         raise SystemExit('No test files found')
     ci_info['token'] = token
     with tempfile.NamedTemporaryFile() as fd:
-        with tarfile.open(fd.name, 'w:gz') as tar:
+        with tarfile.open(fileobj=fd, mode='w:gz') as tar:
             for filename in files:
                 tar.add(filename)
+        fd.seek(0)
         ci_info = {k: v for (k, v) in ci_info.items() if v}
         params = ci_info and '?' + urlencode(ci_info) or ''
         result = urlopen(server + '/api/v1/upload' + params, data=fd)