Topic/default/windows test fixes

The remaining issue is a ton of these failures in test-check-compat-strings.t:

--- c:/Users/Matt/hg-evolve/tests/test-check-compat-strings.t
+++ c:/Users/Matt/hg-evolve/tests/test-check-compat-strings.t.err
@@ -7,3 +7,493 @@

   $ "$PYTHON" "$TESTDIR/testlib/check-compat-strings.py" \
   > "$TESTDIR/../hgext3rd/" "$RUNTESTDIR/.."
+  Error processing line 7 of C:\Python2717\lib\site-packages\pywin32.pth:
+
+    Traceback (most recent call last):
+      File "C:\Python2717\Lib\site.py", line 152, in addpackage
+        exec line
+      File "<string>", line 1, in <module>
+      File "C:\Python2717\lib\site-packages\win32\lib\pywin32_bootstrap.py", line 30, in <module>
+        os.environ["PATH"] = pywin32_system32 + os.pathsep + os.environ["PATH"]
+      File "C:\Python2717\Lib\os.py", line 425, in __getitem__
+        return self.data[key.upper()]
+    KeyError: 'PATH'
+
+  Remainder of file ignored
+  obsolete feature not enabled but 217326 markers found!

The content of the file is:

$ cat "C:\Python2717\lib\site-packages\pywin32.pth"
# .pth file for the PyWin32 extensions
win32
win32\lib
Pythonwin
# And some hackery to deal with environments where the post_install script
# isn't run.
import pywin32_bootstrap

So IDK if there's a way to skip this if pywin32 is installed, or what. I think the variable is cased as Path, and I thought os.environ played games to make it case insensitive.