Tenacity repr() KeyError

teancity_repr_key_error.diff

diff --git a/tenacity/__init__.py b/tenacity/__init__.py
index ef516e7..61291cc 100644
--- a/tenacity/__init__.py
+++ b/tenacity/__init__.py
@@ -125,13 +125,19 @@ class BaseRetrying(object):
         self._local = threading.local()

     def __repr__(self):
-        attrs = dict(
-            _utils.visible_attrs(self, attrs={'me': id(self)}),
-            __class__=self.__class__.__name__,
-        )
-        return ("<%(__class__)s object at 0x%(me)x (stop=%(stop)s, "
-                "wait=%(wait)s, sleep=%(sleep)s, retry=%(retry)s, "
-                "before=%(before)s, after=%(after)s)>") % (attrs)
+        possible_attrs = ('stop', 'wait', 'sleep', 'retry', 'before', 'after')
+        visible_attrs = _utils.visible_attrs(self)
+        attrs_repr_list = []
+        for attr in possible_attrs:
+            value = visible_attrs.get(attr)
+            if value is None:
+                continue
+            attrs_repr_list.append('%s=%s' % (attr, value))
+        context = dict(
+            attrs=', '.join(attrs_repr_list),
+            me=id(self),
+            __class__=self.__class__.__name__)
+        return "<%(__class__)s object at 0x%(me)x (%(attrs)s)>" % context

     @property
     def statistics(self):
diff --git a/tenacity/tests/test_tenacity.py b/tenacity/tests/test_tenacity.py
index b14cb6e..786d729 100644
--- a/tenacity/tests/test_tenacity.py
+++ b/tenacity/tests/test_tenacity.py
@@ -20,6 +20,7 @@ import unittest

 import tenacity
 from tenacity import retry
+from tenacity import BaseRetrying
 from tenacity import RetryError
 from tenacity import Retrying

@@ -757,5 +758,14 @@ class TestStatistics(unittest.TestCase):
         self.assertEqual(2, _foobar.retry.statistics['attempt_number'])


+class TestMisc(unittest.TestCase):
+    def test_repr(self):
+        class CustomRetrying(BaseRetrying):
+            pass
+
+        repr(Retrying())
+        repr(CustomRetrying())
+
+
 if __name__ == '__main__':
     unittest.main()