Fix current/active server deletability validation

https://bugzilla.redhat.com/show_bug.cgi?id=1575077

Note, the UI will need to check server.errors after attempting to
destroy the record to see any errors.

app/models/miq_server.rb

@@ -249,8 +249,7 @@ def self.check_migrations_up_to_date
 
   def validate_is_deleteable
     unless self.is_deleteable?
-      _log.error(@error_message)
-      @error_message = nil
+      _log.error(@errors.full_messages)
       throw :abort
     end
   end
@@ -492,13 +491,17 @@ def is_recently_active?
 
   def is_deleteable?
     if self.is_local?
-      @error_message = N_("Cannot delete currently used %{log_message}") % {:log_message => format_short_log_msg}
+      message = N_("Cannot delete currently used %{log_message}") % {:log_message => format_short_log_msg}
+      @errors ||= ActiveModel::Errors.new(self)
+      @errors.add(:base, message)
       return false
     end
     return true if self.stopped?
 
     if is_recently_active?
-      @error_message = N_("Cannot delete recently active %{log_message}") % {:log_message => format_short_log_msg}
+      message = N_("Cannot delete recently active %{log_message}") % {:log_message => format_short_log_msg}
+      @errors ||= ActiveModel::Errors.new(self)
+      @errors.add(:base, message)
       return false
     end
 

spec/models/miq_server_spec.rb

@@ -156,6 +156,23 @@
       end
     end
 
+    context "validate_is_deleteable before destroying" do
+      it "prevents deleting the current server" do
+        allow(@miq_server).to receive(:is_local?).and_return(true)
+        @miq_server.destroy
+
+        expect(@miq_server.errors.full_messages.first).to match(/current/)
+      end
+
+      it "prevents deleting recently active server" do
+        allow(@miq_server).to receive(:is_local?).and_return(false)
+        @miq_server.last_heartbeat = 2.minutes.ago.utc
+        @miq_server.destroy
+
+        expect(@miq_server.errors.full_messages.first).to match(/recently/)
+      end
+    end
+
     context "#ntp_reload_queue" do
       let(:queue_cond) { {:method_name => 'ntp_reload', :class_name => 'MiqServer', :instance_id => @miq_server.id, :server_guid => @miq_server.guid, :zone => @miq_server.zone.name} }
       let(:message)    { MiqQueue.where(queue_cond).first }