catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I0bb9caa5bff2c57ea331b9982f279753c44d69d4
diff --git a/vpd_tool_impl.cpp b/vpd_tool_impl.cpp
index 5d35f03..a7cc205 100644
--- a/vpd_tool_impl.cpp
+++ b/vpd_tool_impl.cpp
@@ -301,7 +301,7 @@
                         output.insert(j.begin(), j.end());
                     }
                 }
-                catch (exception& e)
+                catch (const exception& e)
                 {
                     cerr << e.what();
                 }
@@ -355,7 +355,7 @@
 
         debugger(output);
     }
-    catch (json::exception& e)
+    catch (const json::exception& e)
     {
         json output = json::object({});
         json kwVal = json::object({});
@@ -445,7 +445,7 @@
         }
         edit.updateKeyword(val, updCache);
     }
-    catch (json::parse_error& ex)
+    catch (const json::parse_error& ex)
     {
         throw(VpdJsonException("Json Parsing failed", INVENTORY_JSON_SYM_LINK));
     }