--- a/tests/hghave	Tue Feb 06 12:12:49 2018 -0600
+++ b/tests/hghave	Tue Feb 06 16:34:28 2018 -0800
@@ -3,25 +3,29 @@
 if all features are there, non-zero otherwise. If a feature name is
 prefixed with "no-", the absence of feature is tested.
 """
+
+from __future__ import absolute_import, print_function
+
+import hghave
 import optparse
+import os
 import sys
-import hghave
 
 checks = hghave.checks
 
 def list_features():
-    for name, feature in checks.iteritems():
+    for name, feature in sorted(checks.items()):
         desc = feature[1]
-        print name + ':', desc
+        print(name + ':', desc)
 
 def test_features():
     failed = 0
-    for name, feature in checks.iteritems():
+    for name, feature in checks.items():
         check, _ = feature
         try:
             check()
-        except Exception, e:
-            print "feature %s failed:  %s" % (name, e)
+        except Exception as e:
+            print("feature %s failed:  %s" % (name, e))
             failed += 1
     return failed
 
@@ -30,11 +34,31 @@
                   help="test available features")
 parser.add_option("--list-features", action="store_true",
                   help="list available features")
-parser.add_option("-q", "--quiet", action="store_true",
-                  help="check features silently")
+
+def _loadaddon():
+    if 'TESTDIR' in os.environ:
+        # loading from '.' isn't needed, because `hghave` should be
+        # running at TESTTMP in this case
+        path = os.environ['TESTDIR']
+    else:
+        path = '.'
+
+    if not os.path.exists(os.path.join(path, 'hghaveaddon.py')):
+        return
+
+    sys.path.insert(0, path)
+    try:
+        import hghaveaddon
+        assert hghaveaddon  # silence pyflakes
+    except BaseException as inst:
+        sys.stderr.write('failed to import hghaveaddon.py from %r: %s\n'
+                         % (path, inst))
+        sys.exit(2)
+    sys.path.pop(0)
 
 if __name__ == '__main__':
     options, args = parser.parse_args()
+    _loadaddon()
     if options.list_features:
         list_features()
         sys.exit(0)
@@ -42,36 +66,4 @@
     if options.test_features:
         sys.exit(test_features())
 
-    quiet = options.quiet
-
-    failures = 0
-
-    def error(msg):
-        global failures
-        if not quiet:
-            sys.stderr.write(msg + '\n')
-        failures += 1
-
-    for feature in args:
-        negate = feature.startswith('no-')
-        if negate:
-            feature = feature[3:]
-
-        if feature not in checks:
-            error('skipped: unknown feature: ' + feature)
-            continue
-
-        check, desc = checks[feature]
-        try:
-            available = check()
-        except Exception, e:
-            error('hghave check failed: ' + feature)
-            continue
-
-        if not negate and not available:
-            error('skipped: missing feature: ' + desc)
-        elif negate and available:
-            error('skipped: system supports %s' % desc)
-
-    if failures != 0:
-        sys.exit(1)
+    hghave.require(args)