nl_tokens: Retrieves WDA upgrade timestamp
pl_tokens: async function getWDAUpgradeTimestamp ( bootstrapPath ) { const carthageRootPath = path . resolve ( bootstrapPath , CARTHAGE_ROOT ) ; if ( await fs . exists ( carthageRootPath ) ) { const { mtime } = await <mask> . stat ( carthageRootPath ) ; return mtime . getTime ( ) ; } return null ; }