A TestTemplateInvocationContextProvider must not return an empty stream

[t1]

The javadoc of TestTemplateInvocationContextProvider# provideTestTemplateInvocationContexts says: This method is only called by the framework if #supportsTestTemplate previously returned true for the same ExtensionContext. Thus, this method must not return an empty Stream.

But the junit5 PactVerificationInvocationContextProvider returns an empty stream if it doesn't find any pacts. This results in the cryptic error message from JUnit 5: org.junit.platform.commons.PreconditionViolationException: No supporting TestTemplateInvocationContextProvider provided an invocation context

Can we throw an exception instead.

[uglyog]

4.0.6 has been released with this fix