Specify the name of the rule in the "Rule is unimplemented." error.

PiperOrigin-RevId: 750107659
Change-Id: I1a6d4d679ef836190c4adc76cff2676c27098347

Author: Googler

src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java

@@ -644,7 +644,7 @@ public ConfiguredTarget create(RuleContext ruleContext) {
             """
                 .formatted(ruleName, bzlLoadLabel, ruleName));
       } else {
-        ruleContext.ruleError("Rule is unimplemented.");
+        ruleContext.ruleError("Rule '" + ruleName + "' is unimplemented.");
       }
       return null;
     }

src/test/java/com/google/devtools/build/lib/rules/python/PyTestConfiguredTargetTest.java

@@ -95,7 +95,7 @@ public void nativePyTestReportsAnError() throws Exception {
     if (analysisMock.isThisBazel()) {
       assertThat(error).hasMessageThat().contains("name 'py_test' is not defined");
     } else {
-      assertThat(error).hasMessageThat().contains("Rule is unimplemented.");
+      assertThat(error).hasMessageThat().contains("Rule 'py_test' is unimplemented.");
     }
   }
 }