[MISC] Run the continuous writes script with the charm's python (#42)

* Run the continuous writes script with the charm's python rather than machine's python

* Use pathlib instead of os.path

* Specify python directly instead of using pathlib

Author: shayancanonical

src/charm.py

@@ -186,7 +186,7 @@ def _start_continuous_writes(self, starting_number: int) -> None:
         self._stop_continuous_writes()
 
         command = [
-            "/usr/bin/python3",
+            "venv/bin/python",
             "src/continuous_writes.py",
             self._database_config["user"],
             self._database_config["password"],