diff --git a/lldb/packages/Python/lldbsuite/test/lldbtest.py b/lldb/packages/Python/lldbsuite/test/lldbtest.py
--- a/lldb/packages/Python/lldbsuite/test/lldbtest.py
+++ b/lldb/packages/Python/lldbsuite/test/lldbtest.py
@@ -426,7 +426,7 @@
         process = Popen(
             shellCommand,
             stdout=PIPE,
-            stderr=PIPE,
+            stderr=STDOUT,
             shell=True,
             **kwargs)
         pid = process.pid
diff --git a/lldb/packages/Python/lldbsuite/test_event/build_exception.py b/lldb/packages/Python/lldbsuite/test_event/build_exception.py
--- a/lldb/packages/Python/lldbsuite/test_event/build_exception.py
+++ b/lldb/packages/Python/lldbsuite/test_event/build_exception.py
@@ -4,8 +4,7 @@
         super(BuildError, self).__init__("Error when building test subject")
         self.command = called_process_error.lldb_extensions.get(
             "command", "<command unavailable>")
-        self.build_error = called_process_error.lldb_extensions.get(
-            "stderr_content", "<error output unavailable>")
+        self.build_error = called_process_error.lldb_extensions["stdout_content"]
 
     def __str__(self):
         return self.format_build_error(self.command, self.build_error)