change many str(e) to repr(e) as some exceptions were cryptic

it's often valuable to see the type of the exception
(especially as for some exceptions str(e) == '')

electrum/plugins/keepkey/keepkey.py

@@ -216,7 +216,7 @@ class KeepKeyPlugin(HW_PluginBase):
             exit_code = 1
         except BaseException as e:
             self.logger.exception('')
-            handler.show_error(str(e))
+            handler.show_error(repr(e))
             exit_code = 1
         finally:
             wizard.loop.exit(exit_code)