bitbake: data_smart: Simplify ExpansionError exception

This seemingly convoluted syntax doesn't work in python3. Instead
use the chained exception handling syntax which appears to make more
sense here.

(Bitbake rev: b19a4c5166303b1fa680582adf63e6a5564bfb4c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -397,8 +397,7 @@ class DataSmart(MutableMapping):
             except bb.parse.SkipRecipe:
                 raise
             except Exception as exc:
-                exc_class, exc, tb = sys.exc_info()
-                raise ExpansionError, ExpansionError(varname, s, exc), tb
+                raise ExpansionError(varname, s, exc) from exc
 
         varparse.value = s