Use simpler code for tests for expected failures

[traylenator]

Pull Request (PR) description

Rather than:

 it { is_expected.to raise_error(Puppet::PreformattedError,
       `%r{Package name must be formatted as Yum::RpmName, not 'String'}
      )
 }

use

it { is_expected.to compile.and_raise_error(
   %r{Package name must be formatted as Yum::RpmName, not 'String'}
)}