LSB Error code support for status and exit. Fixes Supervisor#24

* error_status being set in supervisorctl.py raises a SystemExit of that code on exit.
* handle_error wraps all error output and sets error_status if not in interactive mode.
* onecmd is the entry point for single command and where we enforce SystemExit.

Author: lukeweber

supervisor/options.py

@@ -1579,6 +1579,7 @@ class ClientOptions(Options):
     username = None
     password = None
     history_file = None
+    exit_on_error = None
 
     def __init__(self):
         Options.__init__(self, require_configfile=False)
@@ -1591,6 +1592,9 @@ def __init__(self):
         self.configroot.supervisorctl.password = None
         self.configroot.supervisorctl.history_file = None
 
+        # Set to 0 because it's only activated in realize() if not in interactive mode.
+        self.configroot.supervisorctl.exit_on_error = 0
+
         from supervisor.supervisorctl import DefaultControllerPlugin
         default_factory = ('default', DefaultControllerPlugin, {})
         # we always add the default factory. If you want to a supervisorctl
@@ -1611,6 +1615,8 @@ def realize(self, *arg, **kw):
         if not self.args:
             self.interactive = 1
 
+        self.exit_on_error = 0 if self.interactive else 1
+
     def read_config(self, fp):
         section = self.configroot.supervisorctl
         need_close = False