--- a/mercurial/sslutil.py	Thu Oct 12 19:20:04 2017 -0700
+++ b/mercurial/sslutil.py	Thu Oct 12 23:30:46 2017 -0700
@@ -477,7 +477,7 @@
                         'for more info)\n'))
 
             elif (e.reason == 'CERTIFICATE_VERIFY_FAILED' and
-                pycompat.osname == 'nt'):
+                pycompat.iswindows):
 
                 ui.warn(_('(the full certificate chain may not be available '
                           'locally; see "hg help debugssl")\n'))
@@ -717,7 +717,7 @@
     # because we'll get a certificate verification error later and the lack
     # of loaded CA certificates will be the reason why.
     # Assertion: this code is only called if certificates are being verified.
-    if pycompat.osname == 'nt':
+    if pycompat.iswindows:
         if not _canloaddefaultcerts:
             ui.warn(_('(unable to load Windows CA certificates; see '
                       'https://mercurial-scm.org/wiki/SecureConnections for '
@@ -749,7 +749,7 @@
     # / is writable on Windows. Out of an abundance of caution make sure
     # we're not on Windows because paths from _systemcacerts could be installed
     # by non-admin users.
-    assert pycompat.osname != 'nt'
+    assert not pycompat.iswindows
 
     # Try to find CA certificates in well-known locations. We print a warning
     # when using a found file because we don't want too much silent magic