lib: Fix silent assertitons

There are a couple of assert statements in the codebase which can make jw-pkg fail without any detail whatsoever if --backtrace is not specified, fix that.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/App.py

@@ -145,7 +145,9 @@ class App: # export
         except Exception as e:
             log(ERR, 'Failed: {}'.format(repr(e) if self.__back_trace else str(e)))
             exit_status = 1
-            if self.__back_trace:
+            # AssertionErrors are programming errors, hence a programmer should
+            # get a chance to figure it out
+            if self.__back_trace or isinstance(e, AssertionError):
                 raise
         finally:
             if pr is not None: