[feature request] improve error message in order to up efficiency.

[rambohe-ch]

What would you like to be added:
When unit tests failed, we need to search the keyword fail to find out the failed cases, but there are many error messages that include keyword fail(such as in the following image), this will affect our efficiency in finding failed cases.

so i think we can improve the error messages, this means change word fail to couldn't as following:

failed to update the DynamicRESTMapper failed to update cached dynamic RESTMapper, path does not exist --> could not update the DynamicRESTMapper failed to update cached dynamic RESTMapper, path does not exist

others
/kind feature

[dzcvxe]

/assign