Detected a dynamic value being used with urllib. urllib supports 'file://' schemes, so a dynamic value controlled by a malicious actor may allow them to read arbitrary files. Audit uses of urllib calls to ensure user data cannot control the URLs, or consider using the 'requests' library instead.
df = urllib.request.urlopen('https://poloniex.com/public?command=' + "returnChartData" + '&currencyPair=' + str(pairing) + str(ticker) + '&start=' + str(start) + '&end=' + str(end) +'&period=' + str(period))