Add changelog entry

docs/changes/2175.api.rst

@@ -0,0 +1,12 @@
+Change default behaviour of `run_rool`:
+
+1. The default value of `raises` is now `True`. That means, when using
+   `run_tool`, the Exceptions raised by a Tool will be re-raised. The raised
+   exceptions can be tested for their type and content.
+   If the Tool must fail and only the non-zero error case is important to test,
+   set `raises=False` (as it was before).
+
+2. If the `cwd` parameter is `None` (as per default), now a temporary directory
+   is used instead of the directory, where `run_tool` is called (typically via
+   pytest). This way, log-files and other output files don't clutter your
+   working space.