--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/thirdparty/attr/_compat.py	Sun Oct 01 04:14:16 2017 -0700
@@ -0,0 +1,90 @@
+from __future__ import absolute_import, division, print_function
+
+import sys
+import types
+
+
+PY2 = sys.version_info[0] == 2
+
+
+if PY2:
+    from UserDict import IterableUserDict
+
+    # We 'bundle' isclass instead of using inspect as importing inspect is
+    # fairly expensive (order of 10-15 ms for a modern machine in 2016)
+    def isclass(klass):
+        return isinstance(klass, (type, types.ClassType))
+
+    # TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
+    TYPE = "type"
+
+    def iteritems(d):
+        return d.iteritems()
+
+    def iterkeys(d):
+        return d.iterkeys()
+
+    # Python 2 is bereft of a read-only dict proxy, so we make one!
+    class ReadOnlyDict(IterableUserDict):
+        """
+        Best-effort read-only dict wrapper.
+        """
+
+        def __setitem__(self, key, val):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise TypeError("'mappingproxy' object does not support item "
+                            "assignment")
+
+        def update(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError("'mappingproxy' object has no attribute "
+                                 "'update'")
+
+        def __delitem__(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise TypeError("'mappingproxy' object does not support item "
+                            "deletion")
+
+        def clear(self):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError("'mappingproxy' object has no attribute "
+                                 "'clear'")
+
+        def pop(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError("'mappingproxy' object has no attribute "
+                                 "'pop'")
+
+        def popitem(self):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError("'mappingproxy' object has no attribute "
+                                 "'popitem'")
+
+        def setdefault(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError("'mappingproxy' object has no attribute "
+                                 "'setdefault'")
+
+        def __repr__(self):
+            # Override to be identical to the Python 3 version.
+            return "mappingproxy(" + repr(self.data) + ")"
+
+    def metadata_proxy(d):
+        res = ReadOnlyDict()
+        res.data.update(d)  # We blocked update, so we have to do it like this.
+        return res
+
+else:
+    def isclass(klass):
+        return isinstance(klass, type)
+
+    TYPE = "class"
+
+    def iteritems(d):
+        return d.items()
+
+    def iterkeys(d):
+        return d.keys()
+
+    def metadata_proxy(d):
+        return types.MappingProxyType(dict(d))