URLHeadBear: fake the user agent

A random fake user agent is used to request webpages
that do not allow bot visits.

Fixes #1203

bears/general/URLHeadBear.py

@@ -1,5 +1,6 @@
 import requests
 from urllib.parse import urlparse
+from fake_useragent.fake import UserAgent
 
 from bears.general.URLBear import URLBear, LINK_CONTEXT
 
@@ -82,8 +83,9 @@ def check_prerequisites(cls):
     @staticmethod
     def get_head_response(url, timeout):
         try:
+            headers = {'User-Agent': UserAgent().random}
             head_resp = requests.head(url, allow_redirects=False,
-                                      timeout=timeout)
+                                      headers=headers, timeout=timeout)
             return head_resp
         except requests.exceptions.RequestException as exc:
             return exc