fix: include package name in exception messages

Add package name context to exception formatting to identify which
package failed during build errors. The package name is added by
FromagerLogRecord when messages are logged, and _format_exception
handles formatting chained exceptions with 'because' syntax.

Improve parallel build error handling to preserve package context
across thread boundaries using RuntimeError wrapper.

Tests added to test_external_commands.py verify error logging and
exception formatting include package names and handle chained exceptions.

Update e2e test pattern to match new log format that includes package names.

Closes: #845
Signed-off-by: Andre Lustosa <alustosa@redhat.com>

Author: andre-motta

e2e/test_bootstrap_constraints.sh

@@ -28,7 +28,7 @@ fromager \
 pass=true
 
 # Check for log message that the override is loaded
-if ! grep -q "ERROR: Unable to resolve requirement specifier stevedore==5.2.0 with constraint stevedore==4.0.0" "$OUTDIR/bootstrap.log"; then
+if ! grep -q "ERROR.*stevedore: Unable to resolve requirement specifier stevedore==5.2.0 with constraint stevedore==4.0.0" "$OUTDIR/bootstrap.log"; then
   echo "FAIL: did not throw expected error when constraint and requirement conflict" 1>&2
   pass=false
 fi

src/fromager/__main__.py

@@ -275,7 +275,7 @@ def invoke_main() -> None:
             err,
             exc_info=True,
         )  # log the full traceback details to the debug log file, if any
-        logger.error(f"ERROR: {_format_exception(err)}")
+        logger.error(_format_exception(err))
         if _DEBUG:
             raise
         sys.exit(1)

src/fromager/commands/build.py

@@ -680,14 +680,15 @@ def update_progressbar_cb(future: concurrent.futures.Future) -> None:
                     try:
                         entry = future.result()
                     except Exception as e:
-                        logger.error("failed to build: %s", e)
-                        raise
+                        logger.error(f"Failed to build {node.key}: {e}")
+                        raise RuntimeError(f"Failed to build {node.key}") from e
                     else:
                         # success
                         built_entries.append(entry)
                     finally:
                         # mark node as done, progress bar is updated in callback.
                         topo.done(node)
+                        # Re-raise with package context since context var is lost across threads
 
     metrics.summarize(wkctx, "Building in parallel")
     _summary(wkctx, built_entries)

src/fromager/commands/download_sequence.py

@@ -83,7 +83,8 @@ def download_one(entry: dict[str, typing.Any]):
             except Exception as err:
                 logger.error(f"failed to download sdist for {req}: {err}")
                 if not ignore_missing_sdists:
-                    raise
+                    # Re-raise with package context since context var is lost across threads
+                    raise RuntimeError(f"Failed to download sdist for {req}") from err
         else:
             logger.info(
                 f"{entry['dist']}: uses a {entry['source_url_type']} downloader, skipping"

tests/test_external_commands.py

@@ -131,3 +131,48 @@ def test_external_command_output_prefix(caplog: pytest.LogCaptureFixture) -> Non
     finally:
         # Restore the original log record factory
         logging.setLogRecordFactory(old_factory)
+
+
+def test_external_commands_error_includes_package_name(caplog) -> None:
+    """Test that package name is included in error logs when context var is set"""
+    logging.setLogRecordFactory(log.FromagerLogRecord)
+
+    req = Requirement("test-package==1.0.0")
+    version = Version("1.0.0")
+
+    with log.req_ctxvar_context(req, version):
+        with caplog.at_level(logging.ERROR):
+            with pytest.raises(subprocess.CalledProcessError):
+                external_commands.run(["sh", "-c", "exit 1"])
+
+    error_logs = [
+        record.message for record in caplog.records if record.levelname == "ERROR"
+    ]
+    assert len(error_logs) > 0
+    assert any("test-package-1.0.0:" in msg for msg in error_logs), (
+        f"Expected package name in error logs, got: {error_logs}"
+    )
+
+
+def test_format_exception_formats_chained_exceptions() -> None:
+    """Test that _format_exception formats chained exceptions correctly"""
+    from fromager import __main__
+
+    # Test basic exception formatting
+    exception_without_cause = subprocess.CalledProcessError(
+        1, ["command"], output="some output"
+    )
+    message = __main__._format_exception(exception_without_cause)
+    assert "Command '['command']' returned non-zero exit status 1" in message
+
+    # Test chained exception formatting with "because"
+    try:
+        try:
+            raise ValueError("Root cause")
+        except ValueError as e:
+            raise RuntimeError("Higher level error") from e
+    except RuntimeError as chained_exc:
+        formatted = __main__._format_exception(chained_exc)
+        assert "Higher level error" in formatted
+        assert "because" in formatted
+        assert "Root cause" in formatted