Fix usage of bare 'except'

flake8 reports:

  E722 do not use bare 'except'

Replace them with 'except Exception' per [1] which says:

  Bare except will catch exceptions you almost certainly don't want
  to catch, including KeyboardInterrupt (the user hitting Ctrl+C) and
  Python-raised errors like SystemExit

  If you don't have a specific exception you're expecting, at least
  except Exception, which is the base type for all "Regular" exceptions.

[1] https://stackoverflow.com/a/54948581

Change-Id: Ic555ea9482645899f5b04040ddb6b24eadbf9062
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254606
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>

main.py

@@ -364,7 +364,7 @@ class _BasicAuthHandler(urllib.request.HTTPBasicAuthHandler):
       req.add_header = _add_header
       return urllib.request.AbstractBasicAuthHandler.http_error_auth_reqed(
           self, authreq, host, req, headers)
-    except:
+    except Exception:
       reset = getattr(self, 'reset_retry_count', None)
       if reset is not None:
         reset()
@@ -389,7 +389,7 @@ class _DigestAuthHandler(urllib.request.HTTPDigestAuthHandler):
       req.add_header = _add_header
       return urllib.request.AbstractDigestAuthHandler.http_error_auth_reqed(
           self, auth_header, host, req, headers)
-    except:
+    except Exception:
       reset = getattr(self, 'reset_retry_count', None)
       if reset is not None:
         reset()
@@ -432,7 +432,7 @@ class _KerberosAuthHandler(urllib.request.BaseHandler):
         return response
     except kerberos.GSSError:
       return None
-    except:
+    except Exception:
       self.reset_retry_count()
       raise
     finally: