Make import_test.py debuggable from console output. (keras-team#21033)

Previously, if no wheel was found, the `[-1]` subscript would fail, preventing the `if not whl_path` clause from outputting the error message.

Author: hertschuh

integration_tests/import_test.py

@@ -28,11 +28,12 @@ def setup_package():
     whl_path = re.findall(
         r"[^\s]*\.whl",
         build_process.stdout,
-    )[-1]
+    )
     if not whl_path:
+        print(build_process.stdout)
         print(build_process.stderr)
         raise ValueError("Installing Keras package unsuccessful. ")
-    return whl_path
+    return whl_path[-1]
 
 
 def create_virtualenv():