Conflict requirement needs to generate dependency.

If there is only conflict requirement, this still menas that there is
dependency on that package and appropriate requirement must be generated
(rhbz#1561487)

ruby.spec

@@ -1067,6 +1067,9 @@ make check TESTS="-v $DISABLE_TESTS"
 %{gem_dir}/specifications/xmlrpc-%{xmlrpc_version}.gemspec
 
 %changelog
+* Tue Apr 10 2018 Vít Ondruch <vondruch@redhat.com> - 2.5.1-92
+- Conflict requirement needs to generate dependency.
+
 * Thu Mar 29 2018 Pavel Valena <pvalena@redhat.com> - 2.5.1-92
 - Update to Ruby 2.5.1.
 

rubygems.req

@@ -11,7 +11,13 @@ module RubyGemsReq
         when '~>'
           expand_pessimistic_requirement(r)
         when '!='
+          # If there is only the conflict requirement, we still need to depend
+          # on the specified gem.
+          if requirements.size == 1
+            Gem::Requirement.default.requirements
+          else
             []
+          end
         else
           [r]
         end