Make Java-implemented Bazel tests able to pass when rules_python is loaded.

The tests don't actually load rules_python when run as Bazel. The rules_python
code is only loaded into the tests when run as part of the internal Google
builds.

PiperOrigin-RevId: 584178944
Change-Id: I7c7dd568bc740b83a42c518456a0f7eaf14bcb16
diff --git a/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java b/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
index b6a0b06..11ad7fa 100644
--- a/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
+++ b/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
@@ -127,6 +127,9 @@
   /** The directory in which rules_cc repo resides in execroot. */
   public static final String RULES_CC_REPOSITORY_EXECROOT = "external/" + RulesCcRepoName.CANONICAL_REPO_NAME + "/";
 
+  /** The repo/package rules_python is rooted at. If empty, builtin rules are used. */
+  public static final String RULES_PYTHON_PACKAGE_ROOT = "";
+
   public static final ImmutableList<String> DOCS_RULES_PATHS = ImmutableList.of(
       "src/main/java/com/google/devtools/build/lib/rules");