diff -r f2c5b9d48b29 -r 7b428b00a1d4 mercurial/commands.py
--- a/mercurial/commands.py	Tue Oct 18 17:44:42 2016 -0700
+++ b/mercurial/commands.py	Wed Oct 19 15:07:11 2016 -0700
@@ -68,6 +68,7 @@
     setdiscovery,
     simplemerge,
     sshserver,
+    sslutil,
     streamclone,
     templatekw,
     templater,
@@ -2703,6 +2704,25 @@
     fm.write('pythonlib', _("checking Python lib (%s)...\n"),
              os.path.dirname(os.__file__))
 
+    security = set(sslutil.supportedprotocols)
+    if sslutil.hassni:
+        security.add('sni')
+
+    fm.write('pythonsecurity', _("checking Python security support (%s)\n"),
+             fm.formatlist(sorted(security), name='protocol',
+                           fmt='%s', sep=','))
+
+    # These are warnings, not errors. So don't increment problem count. This
+    # may change in the future.
+    if 'tls1.2' not in security:
+        fm.plain(_('  TLS 1.2 not supported by Python install; '
+                   'network connections lack modern security\n'))
+    if 'sni' not in security:
+        fm.plain(_('  SNI not supported by Python install; may have '
+                   'connectivity issues with some servers\n'))
+
+    # TODO print CA cert info
+
     # hg version
     hgver = util.version()
     fm.write('hgver', _("checking Mercurial version (%s)\n"),