skip mbr update on s390 (bnc#937015)

src/lib/bootloader/mbr_update.rb

@@ -19,6 +19,8 @@ class MBRUpdate
     # Update contents of MBR (active partition and booting code)
     # @return [Boolean] true on success
     def run
+      return true if Yast::Arch.s390
+
       activate = Yast::BootCommon.globals["activate"] == "true"
       generic_mbr = Yast::BootCommon.globals["generic_mbr"] == "true"
 

test/mbr_update_test.rb

@@ -20,6 +20,9 @@
         dev + num.to_s
       end
 
+      # by default common architecture"
+      allow(Yast::Arch).to receive(:architecture).and_return("x86_64")
+
       # fake query for gpt label
       allow(Yast::Storage).to receive(:GetTargetMap).and_return(
         double(:fetch => { "label" => "msdos" },
@@ -28,6 +31,16 @@
       )
     end
 
+    context "on s390" do
+      before do
+        allow(Yast::Arch).to receive(:architecture).and_return("s390_64")
+      end
+
+      it "does nothing except returning true" do
+        expect(subject.run).to eq true
+      end
+    end
+
     context "BootCommon.backup_mbr config is not set" do
       before do
         Yast::BootCommon.backup_mbr = false