[IMPR] ignore original exception in BaseSite.__getattr__()

- ignore original exception usually from Family class
  when raising AttributeError in BaseSite.__getattr__()
- also refactor exception message to use f-strings

Change-Id: I119fca320debdaa437c5acb5b61260b5223042c1
---
M pywikibot/site/_basesite.py
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/pywikibot/site/_basesite.py b/pywikibot/site/_basesite.py
index 80dacc7..7142d99 100644
--- a/pywikibot/site/_basesite.py
+++ b/pywikibot/site/_basesite.py
@@ -197,8 +197,8 @@
                 f.__doc__ = method.__doc__
             return f
         except AttributeError:
-            raise AttributeError("{} instance has no attribute '{}'"
-                                 .format(self.__class__.__name__, attr))
+            raise AttributeError(f'{type(self).__name__} instance has no '
+                                 f'attribute {attr!r}') from None
 
     def __str__(self) -> str:
         """Return string representing this Site's name and code."""

