perf python: Avoid shadowing exception name in PostgreSQL exporter

During the perf build, pylint reports:

  ************* Module export-to-postgresql
  python/export-to-postgresql.py:319:8: W0621: Redefining name 'e' from outer scope (line 100) (redefined-outer-name)

Rename 'e' to 'db_error' to clear the warning.

Fixes: b1f968c965 ("perf python: Port export-to-postgresql to perf module")
Reviewed-by: Ian Rogers <irogers@google.com>
Assisted-by: Codex:gpt-6
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/python/export-to-postgresql.py

@@ -316,9 +316,9 @@ class PostgresExporter:
             # SQL identifiers are double-quoted; escape embedded double quotes by doubling them.
             db_name = self.dbname.replace('"', '""')
             self.do_query(f'CREATE DATABASE "{db_name}"')
-        except Exception as e:
+        except Exception as db_error:
             shutil.rmtree(self.output_dir_name, ignore_errors=True)
-            raise e
+            raise db_error
         self.disconnect()
 
         self.connect(self.dbname)