exception: define get_errno for example types

The sdbusplus base exception class now defines a get_errno and
it will become a pure-virtual soon.  Prep for that by defining
function for any of the example exception types (sdbus++ generated
types are already provided).

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I3b2a0e9d356022e1e71ff523eee02ab102d383a2
diff --git a/tools/phosphor-logging/templates/elog-gen-template.mako.hpp b/tools/phosphor-logging/templates/elog-gen-template.mako.hpp
index 0d156ad..878f830 100644
--- a/tools/phosphor-logging/templates/elog-gen-template.mako.hpp
+++ b/tools/phosphor-logging/templates/elog-gen-template.mako.hpp
@@ -133,20 +133,25 @@
     using metadata_types = std::tuple<${meta_string}>;
 
     % if example_yaml:
-    const char* name() const noexcept
+    const char* name() const noexcept override
     {
         return errName;
     }
 
-    const char* description() const noexcept
+    const char* description() const noexcept override
     {
         return errDesc;
     }
 
-    const char* what() const noexcept
+    const char* what() const noexcept override
     {
         return errName;
     }
+
+    int get_errno() const noexcept override
+    {
+        return EIO;
+    }
     % endif
 };