diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -2330,6 +2330,9 @@ class memfilectx(committablefilectx):
         if copied:
             self._copied = (copied, nullid)
 
+    def cmp(self, fctx):
+        return self.data() != fctx.data()
+
     def data(self):
         return self._data
 
diff --git a/mercurial/pure/osutil.py b/mercurial/pure/osutil.py
--- a/mercurial/pure/osutil.py
+++ b/mercurial/pure/osutil.py
@@ -267,7 +267,8 @@ else:
             return self._file.__setattr__(name, value)
 
         def __enter__(self):
-            return self._file.__enter__()
+            self._file.__enter__()
+            return self
 
         def __exit__(self, exc_type, exc_value, exc_tb):
             return self._file.__exit__(exc_type, exc_value, exc_tb)
diff --git a/mercurial/vfs.py b/mercurial/vfs.py
--- a/mercurial/vfs.py
+++ b/mercurial/vfs.py
@@ -525,7 +525,8 @@ class closewrapbase(object):
         return delattr(self._origfh, attr)
 
     def __enter__(self):
-        return self._origfh.__enter__()
+        self._origfh.__enter__()
+        return self
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         raise NotImplementedError('attempted instantiating ' + str(type(self)))
diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -70,7 +70,8 @@ class mixedfilemodewrapper(object):
         object.__setattr__(self, r'_lastop', 0)
 
     def __enter__(self):
-        return self._fp.__enter__()
+        self._fp.__enter__()
+        return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         self._fp.__exit__(exc_type, exc_val, exc_tb)
@@ -132,7 +133,10 @@ class fdproxy(object):
         self._fp = fp
 
     def __enter__(self):
-        return self._fp.__enter__()
+        self._fp.__enter__()
+        # Return this wrapper for the context manager so that the name is
+        # still available.
+        return self
 
     def __exit__(self, exc_type, exc_value, traceback):
         self._fp.__exit__(exc_type, exc_value, traceback)
diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -213,11 +213,7 @@ def _posixworker(ui, func, staticargs, a
         waitforworkers()
         signal.signal(signal.SIGCHLD, oldchldhandler)
         selector.close()
-        status = problem[0]
-        if status:
-            if status < 0:
-                os.kill(os.getpid(), -status)
-            sys.exit(status)
+        return problem[0]
     try:
         openpipes = len(pipes)
         while openpipes > 0:
@@ -236,7 +232,11 @@ def _posixworker(ui, func, staticargs, a
         killworkers()
         cleanup()
         raise
-    cleanup()
+    status = cleanup()
+    if status:
+        if status < 0:
+            os.kill(os.getpid(), -status)
+        sys.exit(status)
 
 def _posixexitstatus(code):
     '''convert a posix exit status into the same form returned by
diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -587,6 +587,17 @@ def rename(src, dst):
     shutil.copy(src, dst)
     os.remove(src)
 
+def makecleanable(path):
+    """Try to fix directory permission recursively so that the entire tree
+    can be deleted"""
+    for dirpath, dirnames, _filenames in os.walk(path, topdown=True):
+        for d in dirnames:
+            p = os.path.join(dirpath, d)
+            try:
+                os.chmod(p, os.stat(p).st_mode & 0o777 | 0o700)  # chmod u+rwx
+            except OSError:
+                pass
+
 _unified_diff = difflib.unified_diff
 if PYTHON3:
     import functools
@@ -953,7 +964,13 @@ class Test(unittest.TestCase):
                 (self._testtmp.decode('utf-8'),
                  self._threadtmp.decode('utf-8')))
         else:
-            shutil.rmtree(self._testtmp, True)
+            try:
+                shutil.rmtree(self._testtmp)
+            except OSError:
+                # unreadable directory may be left in $TESTTMP; fix permission
+                # and try again
+                makecleanable(self._testtmp)
+                shutil.rmtree(self._testtmp, True)
             shutil.rmtree(self._threadtmp, True)
 
         if self._usechg: