Add a spec for rb_rescue2 when the arguments are incorrect

(cherry picked from commit adc9bf1)

Author: eregon

spec/ruby/optional/capi/kernel_spec.rb

@@ -403,6 +403,14 @@ def proc_caller
         @s.rb_rescue2(type_error_proc, :no_exc, proc, :exc, ArgumentError, RuntimeError)
       }.should raise_error(Exception, 'custom error')
     end
+
+    ruby_bug "#17305", ""..."2.7" do
+      it "raises TypeError if one of the passed exceptions is not a Module" do
+        -> {
+          @s.rb_rescue2(-> *_ { raise RuntimeError, "foo" }, :no_exc, -> x { x }, :exc, Object.new, 42)
+        }.should raise_error(TypeError, /class or module required/)
+      end
+    end
   end
 
   describe "rb_catch" do