Add constant.py.

Bug: 292453652
Test: ./parse_cts_report.py -r REPORT -d OUTPUT_DIR &&
  ./aggregate_cts_reports.py -r REPORT [REPORT ...] -d OUTPUT_DIR &&
  ./compare_cts_reports.py [-r CTS_REPORTS [CTS_REPORTS ...]] \
  [--folder CTS_REPORTS] --mode {1,2,n} --output-dir OUTPUT_DIR [--csv CSV] [--output-files]
Change-Id: I96a135feb84b8f5e4dad939500865a65c000351d
4 files changed