Error to open failures.json when prometeus metrics are being preapred

[akolotov]

The following exception appears on the terminal when the metrics for the ERC20-to-native bridge are being collecte:

2021-06-05T10:32:13.795Z (+198ms) [checkWorker2] Done x2
2021-06-05T10:32:15.233Z (+0ms) [metricsWorker] calling getPrometheusMetrics()
readFlle { Error: ENOENT: no such file or directory, open './responses/xdai/failures.json'
    at Object.openSync (fs.js:443:3)
    at Object.readFileSync (fs.js:343:35)
    at readFile (/mono/monitor/utils/file.js:6:24)
    at getPrometheusMetrics (/mono/monitor/prometheusMetrics.js:112:23)
    at metricsWorker (/mono/monitor/metricsWorker.js:12:27)
    at Object.<anonymous> (/mono/monitor/metricsWorker.js:20:1)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
  errno: -2,
  syscall: 'open',
  code: 'ENOENT',
  path: './responses/xdai/failures.json' }
2021-06-05T10:32:15.249Z (+16ms) [metricsWorker] Done
Done in 9.54s.