diff -r 20a42325fdef -r 4338f87dbf6f mercurial/scmutil.py
--- a/mercurial/scmutil.py	Wed Nov 23 00:03:11 2016 +0530
+++ b/mercurial/scmutil.py	Thu Nov 24 00:48:40 2016 +0000
@@ -14,6 +14,7 @@
 import os
 import re
 import shutil
+import socket
 import stat
 import tempfile
 import threading
@@ -141,6 +142,108 @@
     else:
         ui.status(_("no changes found\n"))
 
+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. does not handle all exceptions.
+    """
+    try:
+        return func()
+    # Global exception handling, alphabetically
+    # Mercurial-specific first, followed by built-in and library exceptions
+    except error.LockHeld as inst:
+        if inst.errno == errno.ETIMEDOUT:
+            reason = _('timed out waiting for lock held by %s') % inst.locker
+        else:
+            reason = _('lock held by %s') % inst.locker
+        ui.warn(_("abort: %s: %s\n") % (inst.desc or inst.filename, reason))
+    except error.LockUnavailable as inst:
+        ui.warn(_("abort: could not lock %s: %s\n") %
+               (inst.desc or inst.filename, inst.strerror))
+    except error.OutOfBandError as inst:
+        if inst.args:
+            msg = _("abort: remote error:\n")
+        else:
+            msg = _("abort: remote error\n")
+        ui.warn(msg)
+        if inst.args:
+            ui.warn(''.join(inst.args))
+        if inst.hint:
+            ui.warn('(%s)\n' % inst.hint)
+    except error.RepoError as inst:
+        ui.warn(_("abort: %s!\n") % inst)
+        if inst.hint:
+            ui.warn(_("(%s)\n") % inst.hint)
+    except error.ResponseError as inst:
+        ui.warn(_("abort: %s") % inst.args[0])
+        if not isinstance(inst.args[1], basestring):
+            ui.warn(" %r\n" % (inst.args[1],))
+        elif not inst.args[1]:
+            ui.warn(_(" empty string\n"))
+        else:
+            ui.warn("\n%r\n" % util.ellipsis(inst.args[1]))
+    except error.CensoredNodeError as inst:
+        ui.warn(_("abort: file censored %s!\n") % inst)
+    except error.RevlogError as inst:
+        ui.warn(_("abort: %s!\n") % inst)
+    except error.SignalInterrupt:
+        ui.warn(_("killed!\n"))
+    except error.InterventionRequired as inst:
+        ui.warn("%s\n" % inst)
+        if inst.hint:
+            ui.warn(_("(%s)\n") % inst.hint)
+        return 1
+    except error.Abort as inst:
+        ui.warn(_("abort: %s\n") % inst)
+        if inst.hint:
+            ui.warn(_("(%s)\n") % inst.hint)
+    except ImportError as inst:
+        ui.warn(_("abort: %s!\n") % inst)
+        m = str(inst).split()[-1]
+        if m in "mpatch bdiff".split():
+            ui.warn(_("(did you forget to compile extensions?)\n"))
+        elif m in "zlib".split():
+            ui.warn(_("(is your Python install correct?)\n"))
+    except IOError as inst:
+        if util.safehasattr(inst, "code"):
+            ui.warn(_("abort: %s\n") % inst)
+        elif util.safehasattr(inst, "reason"):
+            try: # usually it is in the form (errno, strerror)
+                reason = inst.reason.args[1]
+            except (AttributeError, IndexError):
+                # it might be anything, for example a string
+                reason = inst.reason
+            if isinstance(reason, unicode):
+                # SSLError of Python 2.7.9 contains a unicode
+                reason = reason.encode(encoding.encoding, 'replace')
+            ui.warn(_("abort: error: %s\n") % reason)
+        elif (util.safehasattr(inst, "args")
+              and inst.args and inst.args[0] == errno.EPIPE):
+            pass
+        elif getattr(inst, "strerror", None):
+            if getattr(inst, "filename", None):
+                ui.warn(_("abort: %s: %s\n") % (inst.strerror, inst.filename))
+            else:
+                ui.warn(_("abort: %s\n") % inst.strerror)
+        else:
+            raise
+    except OSError as inst:
+        if getattr(inst, "filename", None) is not None:
+            ui.warn(_("abort: %s: '%s'\n") % (inst.strerror, inst.filename))
+        else:
+            ui.warn(_("abort: %s\n") % inst.strerror)
+    except MemoryError:
+        ui.warn(_("abort: out of memory\n"))
+    except SystemExit as inst:
+        # Commands shouldn't sys.exit directly, but give a return code.
+        # Just in case catch this and and pass exit code to caller.
+        return inst.code
+    except socket.error as inst:
+        ui.warn(_("abort: %s\n") % inst.args[-1])
+
+    return -1
+
 def checknewlabel(repo, lbl, kind):
     # Do not use the "kind" parameter in ui output.
     # It makes strings difficult to translate.