catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If6aba71f482f75143e6d669763b8853db22318cf
diff --git a/phosphor-power-sequencer/src/power_interface.cpp b/phosphor-power-sequencer/src/power_interface.cpp
index 13d0af6..50f5911 100644
--- a/phosphor-power-sequencer/src/power_interface.cpp
+++ b/phosphor-power-sequencer/src/power_interface.cpp
@@ -54,7 +54,7 @@
 
             sdbusplus::message::message(msg).append(pgood);
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }
@@ -87,7 +87,7 @@
 
             sdbusplus::message::message(msg).append(timeout);
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }
@@ -121,7 +121,7 @@
             reply.append(pgood);
             reply.method_return();
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }
@@ -157,7 +157,7 @@
                 fmt::format("callbackSetPgoodTimeout: {}", timeout).c_str());
             pwrObj->setPgoodTimeout(timeout);
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }
@@ -190,7 +190,7 @@
 
             sdbusplus::message::message(msg).append(state);
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }
@@ -231,7 +231,7 @@
 
             m.new_method_return().method_return();
         }
-        catch (sdbusplus::exception_t& e)
+        catch (const sdbusplus::exception_t& e)
         {
             return sd_bus_error_set(error, e.name(), e.description());
         }