profile: properly propagate exception from the sub-context manager

Context manager has a mechanism to control extension propagation. It is not
used by profiling right now, but making the code correct will help prevent bug
in the future.

mercurial/profiling.py

@@ -214,8 +214,10 b' class profile(object):'
             raise
 
     def __exit__(self, exception_type, exception_value, traceback):
+        propagate = None
         if self._profiler is not None:
-            self._profiler.__exit__(exception_type, exception_value, traceback)
+            propagate = self._profiler.__exit__(exception_type, exception_value,
+                                                traceback)
             if self._output == 'blackbox':
                 val = 'Profile:\n%s' % self._fp.getvalue()
                 # ui.log treats the input as a format string,
@@ -223,6 +225,7 b' class profile(object):'
                 val = val.replace('%', '%%')
                 self._ui.log('profile', val)
         self._closefp()
+        return propagate
 
     def _closefp(self):
         if self._fpdoclose and self._fp is not None: