Request error 503, add appropriate headers

[VytM]

This issue is described here.

The bottom line is that Amazon blocks requests that do not come from a legitimate browser.
In order to combat it, we need to add appropriate headers:
headers = {'User-Agent' : 'Mozilla/5.0 (Windows NT 6.1; Win64; x64)'}
req = urllib.request.Request (someUrl, headers=headers)

[VytM]

I did not see that you already have it in consts.py in URL_ADDONS variable.