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
@@ -5,7 +5,7 @@
         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>")
+            "stderr_content", "<error output unavailable>").decode("utf-8") + called_process_error.lldb_extensions.get("stdout_content","<stdout output unavailable>").decode("utf-8")
 
     def __str__(self):
         return self.format_build_error(self.command, self.build_error)
@@ -13,4 +13,4 @@
     @staticmethod
     def format_build_error(command, command_output):
         return "Error when building test subject.\n\nBuild Command:\n{}\n\nBuild Command Output:\n{}".format(
-            command, command_output.decode("utf-8"))
+            command, command_output)
diff --git a/lldb/packages/Python/lldbsuite/test_event/formatter/xunit.py b/lldb/packages/Python/lldbsuite/test_event/formatter/xunit.py
--- a/lldb/packages/Python/lldbsuite/test_event/formatter/xunit.py
+++ b/lldb/packages/Python/lldbsuite/test_event/formatter/xunit.py
@@ -258,7 +258,7 @@
         build_issue_description = self._replace_invalid_xml(
             BuildError.format_build_error(
                 test_event.get("build_command", "<None>"),
-                test_event.get("build_error", "<None>")))
+                test_event.get("build_error", "<None>").decode("utf-8")))
 
         result = self._common_add_testcase_entry(
             test_event,