Set exit code on script errors.

Only handle the issue related to .py scripts.

1. interactiveshell: The method safe_execfile is not totally safe now. Errors of user scripts  are raised to a higher level, where we can decide what to do.

2. execution: The %run magic catches exceptions from safe_execfile.

3. shellapp: The _run_cmd_line_code method catches exceptions from safe_execfile and sets the right exit status.

Partial-revert:

1. Change execution.py back.

2. Revert some changes in safe_execfile, then modify the excetion
handling logic.

IPython/core/interactiveshell.py

@@ -2675,10 +2675,11 b' class InteractiveShell(SingletonConfigurable):'
                 # 0
                 # For other exit status, we show the exception unless
                 # explicitly silenced, but only in short form.
-                if kw['raise_exceptions']:
-                    raise
-                if status.code and not kw['exit_ignore']:
-                    self.showtraceback(exception_only=True)
+                if status.code:
+                    if kw['raise_exceptions']:
+                        raise
+                    if not kw['exit_ignore']:
+                        self.showtraceback(exception_only=True)
             except:
                 if kw['raise_exceptions']:
                     raise

IPython/core/shellapp.py

@@ -345,7 +345,8 b' class InteractiveShellApp(Configurable):'
                         # default to python, even without extension
                         self.shell.safe_execfile(full_filename,
                                                  self.shell.user_ns,
-                                                 shell_futures=shell_futures)
+                                                 shell_futures=shell_futures,
+                                                 raise_exceptions=True)
         finally:
             sys.argv = save_argv
 
@@ -415,9 +416,8 b' class InteractiveShellApp(Configurable):'
             try:
                 self._exec_file(fname, shell_futures=True)
             except:
-                self.log.warn("Error in executing file in user namespace: %s" %
-                              fname)
-                self.shell.showtraceback()
+                self.shell.showtraceback(tb_offset=4)
+                self.exit(1)
 
     def _run_module(self):
         """Run module specified at the command-line."""