Don't spam a stacktrace on requests.ConnectionError

ConnectionErrors are expected and not something we can fix. The
exception handler that was catching these previously is a catchall
intended to stop EDMC as a whole from crashing from something
unexpected.

Closes #1082

EDMarketConnector.py

@@ -979,6 +979,11 @@ class AppWindow(object):
             companion.session.invalidate()
             self.login()
 
+        except companion.ServerConnectionError as e:
+            logger.debug(f'Exception while contacting server: {e}')
+            err = self.status['text'] = str(e)
+            play_bad = True
+
         except Exception as e:  # Including CredentialsError, ServerError
             logger.debug('"other" exception', exc_info=e)
             err = self.status['text'] = str(e)

companion.py

@@ -17,6 +17,7 @@ import random
 import time
 import urllib.parse
 import webbrowser
+import socket
 from builtins import object, range, str
 from email.utils import parsedate
 from os.path import join
@@ -170,6 +171,10 @@ class ServerError(Exception):
             self.args = (_("Error: Frontier CAPI didn't respond"),)
 
 
+class ServerConnectionError(ServerError):
+    """Exception class for CAPI connection errors."""
+
+
 class ServerLagging(Exception):
     """Exception Class for CAPI Server lagging.
 
@@ -537,6 +542,10 @@ class Session(object):
             logger.trace('Trying...')
             r = self.session.get(self.server + endpoint, timeout=timeout)  # type: ignore
 
+        except requests.ConnectionError as e:
+            logger.debug(f'Unable to resolve name for CAPI: {e} (for request: {endpoint})')
+            raise ServerConnectionError(f'Unable to connect to endpoint {endpoint}') from e
+
         except Exception as e:
             logger.debug('Attempting GET', exc_info=e)
             raise ServerError(f'{_("Frontier CAPI query failure")}: {endpoint}') from e