catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If6aba71f482f75143e6d669763b8853db22318cf
diff --git a/phosphor-power-supply/psu_manager.hpp b/phosphor-power-supply/psu_manager.hpp
index 68dd091..d95caa3 100644
--- a/phosphor-power-supply/psu_manager.hpp
+++ b/phosphor-power-supply/psu_manager.hpp
@@ -92,7 +92,7 @@
                 runValidateConfig = true;
             }
         }
-        catch (std::exception& e)
+        catch (const std::exception& e)
         {
             log<level::INFO>("Failed to get power state. Assuming it is off.");
             powerOn = false;