[JENKINS-36193] Raise exception when trying to build a job that is disabled.

core/src/main/java/jenkins/model/ParameterizedJobMixIn.java

@@ -52,7 +52,7 @@ import java.util.Map;
 import javax.annotation.CheckForNull;
 import javax.servlet.ServletException;
 import static javax.servlet.http.HttpServletResponse.SC_CREATED;
-import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
+import static javax.servlet.http.HttpServletResponse.SC_CONFLICT;
 import jenkins.util.TimeDuration;
 import org.kohsuke.accmod.Restricted;
 import org.kohsuke.accmod.restrictions.NoExternalUse;
@@ -178,7 +178,7 @@ public abstract class ParameterizedJobMixIn<JobT extends Job<JobT, RunT> & Param
         }
 
         if (!asJob().isBuildable()) {
-            throw HttpResponses.error(SC_INTERNAL_SERVER_ERROR, new IOException(asJob().getFullName() + " is not buildable"));
+            throw HttpResponses.error(SC_CONFLICT, new IOException(asJob().getFullName() + " is not buildable"));
         }
 
         // if a build is parameterized, let that take over
@@ -215,6 +215,9 @@ public abstract class ParameterizedJobMixIn<JobT extends Job<JobT, RunT> & Param
         hudson.model.BuildAuthorizationToken.checkPermission(asJob(), asJob().getAuthToken(), req, rsp);
 
         ParametersDefinitionProperty pp = asJob().getProperty(ParametersDefinitionProperty.class);
+        if (!asJob().isBuildable()) {
+            throw HttpResponses.error(SC_CONFLICT, new IOException(asJob().getFullName() + " is not buildable!"));
+        }
         if (pp != null) {
             pp.buildWithParameters(req, rsp, delay);
         } else {