[rubygems/rubygems] Avoid openssl bug in test_verify_certificate_extra_message

OpenSSL::X509::StoreContext#current_cert returns an empty and invalid
OpenSSL::X509::Certificate instance if it is called before starting a
certificate verification.
https://redirect.github.com/ruby/openssl/pull/919 will change it to
return nil instead in such a case.

Adjust test_verify_certificate_extra_message to actually complete
StoreContext#verify so that it will not rely on this behavior.

ruby/rubygems@823799088d

Author: rhenium

test/rubygems/test_gem_request.rb

@@ -363,19 +363,19 @@ def test_verify_certificate
   def test_verify_certificate_extra_message
     pend if Gem.java_platform?
 
-    error_number = OpenSSL::X509::V_ERR_INVALID_CA
+    error_number = OpenSSL::X509::V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY
 
     store = OpenSSL::X509::Store.new
-    context = OpenSSL::X509::StoreContext.new store
-    context.error = error_number
+    context = OpenSSL::X509::StoreContext.new store, CHILD_CERT
+    context.verify
 
     use_ui @ui do
       Gem::Request.verify_certificate context
     end
 
     expected = <<-ERROR
-ERROR:  SSL verification error at depth 0: invalid CA certificate (#{error_number})
-ERROR:  Certificate  is an invalid CA certificate
+ERROR:  SSL verification error at depth 0: unable to get local issuer certificate (#{error_number})
+ERROR:  You must add #{CHILD_CERT.issuer} to your local trusted store
     ERROR
 
     assert_equal expected, @ui.error