gpio: Raise exception on GPIO lookup failure

This allows dbus calls to gpioInit to fail instead of only returning a
default value. This behavior allows the C-side GPIO lookup to error out
as expected.

Signed-off-by: Xo Wang <xow@google.com>
Change-Id: I13ad20de5d209716f26e46c12ca6941eb3dd5997
diff --git a/pysystemmgr/system_manager.py b/pysystemmgr/system_manager.py
index 6f4bf81..e6bdd29 100644
--- a/pysystemmgr/system_manager.py
+++ b/pysystemmgr/system_manager.py
@@ -161,8 +161,10 @@
         gpio_num = -1
         r = ['', gpio_num, '']
         if name not in System.GPIO_CONFIG:
-            # TODO: Error handling
-            print "ERROR: "+name+" not found in GPIO config table"
+            # TODO: Better error handling
+            msg = "ERROR: "+name+" not found in GPIO config table"
+            print msg
+            raise Exception(msg)
         else:
 
             gpio_num = -1
@@ -173,7 +175,9 @@
                 if 'gpio_pin' in System.GPIO_CONFIG[name]:
                     gpio_num = obmc.system.convertGpio(gpio['gpio_pin'])
                 else:
-                    print "ERROR: SystemManager - GPIO lookup failed for "+name
+                    msg = "ERROR: SystemManager - GPIO lookup failed for "+name
+                    print msg
+                    raise Exception(msg)
 
             if (gpio_num != -1):
                 r = [obmc.enums.GPIO_DEV, gpio_num, gpio['direction']]