Warning popup when encountering network errors

LinkGenerator now handles if the called DomainLinkGenerator children throw request's connection errors in scrape_tags() and informs the user via popup and cancels the scraping.

ArtNet/web/link_generator.py

@@ -1,8 +1,9 @@
-import re
+import logging
 import requests
-import lxml.html
 from urllib.parse import urlparse
 
+from PyQt5.QtWidgets import QMessageBox
+
 DOMAIN_UNKNOWN = -1
 
 
@@ -43,6 +44,10 @@ class DomainIdentifier:
 
 
 class DomainLinkGenerator:
+    """
+    Base class for classes that generate a link to the file on their domain given a sample of a filename pattern and
+    implement a method to scrape the available metadata.
+    """
 
     def __init__(self, domain: DomainIdentifier):
         self.__identifier = domain
@@ -167,7 +172,15 @@ class LinkGenerator:
         for g in self.__link_generators:
             if g.get_identifier() == domain or g.get_domain_name() == url_domain:
                 try:
-                    return g.scrape_tags(url=url, headers=headers, file_name=file_name)
+                    try:
+                        return g.scrape_tags(url=url, headers=headers, file_name=file_name)
+                    except requests.exceptions.ConnectionError as e:
+                        logging.warning(f"Encountered connection error when trying to scrape tags from \"{url}\".\n"
+                                        f"See also:\n{e}")
+                        QMessageBox.warning(None, "Connection Error",
+                                            f"The http connection to \"{url}\" ran into an error. Check your network.\n"
+                                            f"\n{e}")
+                        break
                 except NotImplementedError:
                     pass
         return None