diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -150,7 +150,7 @@ def _runcatch(req):
     except ValueError:
         pass # happens if called in a thread
 
-    try:
+    def _runcatchfunc():
         try:
             debugger = 'pdb'
             debugtrace = {
@@ -212,6 +212,16 @@ def _runcatch(req):
             ui.traceback()
             raise
 
+    return callcatch(ui, _runcatchfunc)
+
+def callcatch(ui, func):
+    """call func() with global exception handling
+
+    return func() if no exception happens. otherwise do some error handling
+    and return an exit code accordingly.
+    """
+    try:
+        return func()
     # Global exception handling, alphabetically
     # Mercurial-specific first, followed by built-in and library exceptions
     except error.AmbiguousCommand as inst:
diff --git a/tests/test-devel-warnings.t b/tests/test-devel-warnings.t
--- a/tests/test-devel-warnings.t
+++ b/tests/test-devel-warnings.t
@@ -91,6 +91,8 @@
    */mercurial/dispatch.py:* in run (glob)
    */mercurial/dispatch.py:* in dispatch (glob)
    */mercurial/dispatch.py:* in _runcatch (glob)
+   */mercurial/dispatch.py:* in callcatch (glob)
+   */mercurial/dispatch.py:* in _runcatchfunc (glob)
    */mercurial/dispatch.py:* in _dispatch (glob)
    */mercurial/dispatch.py:* in runcommand (glob)
    */mercurial/dispatch.py:* in _runcommand (glob)
@@ -125,6 +127,8 @@
    */mercurial/dispatch.py:* in run (glob)
    */mercurial/dispatch.py:* in dispatch (glob)
    */mercurial/dispatch.py:* in _runcatch (glob)
+   */mercurial/dispatch.py:* in callcatch (glob)
+   */mercurial/dispatch.py:* in _runcatchfunc (glob)
    */mercurial/dispatch.py:* in _dispatch (glob)
    */mercurial/dispatch.py:* in runcommand (glob)
    */mercurial/dispatch.py:* in _runcommand (glob)
@@ -147,6 +151,8 @@
    */mercurial/dispatch.py:* in run (glob)
    */mercurial/dispatch.py:* in dispatch (glob)
    */mercurial/dispatch.py:* in _runcatch (glob)
+   */mercurial/dispatch.py:* in callcatch (glob)
+   */mercurial/dispatch.py:* in _runcatchfunc (glob)
    */mercurial/dispatch.py:* in _dispatch (glob)
    */mercurial/dispatch.py:* in runcommand (glob)
    */mercurial/dispatch.py:* in _runcommand (glob)