catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9afd25cfb7f22e4e53a1a58c9a7150c25cfe06b6
diff --git a/src/routing_table.cpp b/src/routing_table.cpp
index 68a9ee3..ab495eb 100644
--- a/src/routing_table.cpp
+++ b/src/routing_table.cpp
@@ -34,7 +34,7 @@
     {
         getRoutes();
     }
-    catch (InternalFailure& e)
+    catch (const InternalFailure& e)
     {
         commit<InternalFailure>();
     }