warn on template rendering errors and continue + --syntax-check option to ifup +

minor parser cleanups

Ticket: CM-2488
Reviewed By:
Testing Done: Tested ifupdown sanity and also the interfaces file in CM-2488

pkg/ifupdownmain.py

@@ -570,7 +570,7 @@ class ifupdownMain(ifupdownBase):
                 self.logger.warning('error saving state (%s)' %str(e))
 
     def up(self, ops, auto=False, allow_classes=None, ifacenames=None,
-           excludepats=None, printdependency=None):
+           excludepats=None, printdependency=None, syntaxcheck=False):
         """ up an interface """
 
         if auto:
@@ -582,6 +582,10 @@ class ifupdownMain(ifupdownBase):
         except Exception:
             raise
 
+        # If only syntax check was requested, return here
+        if syntaxcheck:
+            return
+
         if ifacenames:
             # If iface list is given by the caller, always check if iface
             # is present