Honor combine_stdout_stderr when the result is created from an exception.

Revert a workaround for rustfmt which should no longer be needed.

Test: none
Bug: 379935631
Change-Id: I22263ba77f34067bf6450faa45ae822a18519e2a
Reviewed-on: https://android-review.googlesource.com/c/platform/tools/repohooks/+/3391169
Presubmit-Verified: Treehugger Robot <android-test-infra-workplan-finisher@system.gserviceaccount.com>
Performance: CrystalBall Performance Presubmit <android-crystalball-presubmit-eng@google.com>
Reviewed-by: Tim Bain <tbain@google.com>
Open-Source-Licensing: Lint 🤖 <ayeaye-gerrit@google.com>
Lint: Lint 🤖 <ayeaye-gerrit@google.com>

rh/hooks.py

diff --git a/rh/hooks.py b/rh/hooks.py
index 4d42189..d07e0f9 100644
--- a/rh/hooks.py
+++ b/rh/hooks.py
@@ -1002,8 +1002,7 @@
         # location of the error.
         if result.returncode:
             ret.append(rh.results.HookResult(
-                'rustfmt', project, commit,
-                error=(result.stdout or f'rustfmt failed with status {result.returncode}'),
+                'rustfmt', project, commit, error=result.stdout,
                 files=(d.file,)))
             continue
         # TODO(b/164111102): rustfmt stable does not support --check on stdin.

rh/utils.py

diff --git a/rh/utils.py b/rh/utils.py
index 4f1a063..d4001d6 100644
--- a/rh/utils.py
+++ b/rh/utils.py
@@ -426,7 +426,11 @@
         if e.errno == errno.EACCES:
             estr += '; does the program need `chmod a+x`?'
         if not check:
-            result = CompletedProcess(args=cmd, stderr=estr, returncode=255)
+            result = CompletedProcess(args=cmd, returncode=255)
+            if combine_stdout_stderr:
+                result.stdout = estr
+            else:
+                result.stderr = estr
         else:
             raise CalledProcessError(
                 result.returncode, result.cmd, msg=estr,