CI: Improve logging to find out about any errors when starting CrateDB

Author: amotl

src/crate/testing/layer.py

@@ -294,6 +294,7 @@ def _clean(self):
 
     def start(self):
         self._clean()
+        log.info("Starting process '{}'".format(self.start_cmd))
         self.process = subprocess.Popen(self.start_cmd,
                                         env=self.env,
                                         stdout=subprocess.PIPE)