As env variable not guaranteed, type hint needed to be updated

Author: ArBridgeman

exasol/toolbox/nox/_artifacts.py

@@ -6,6 +6,7 @@
 import sys
 from collections.abc import Iterable
 from pathlib import Path
+from typing import Optional
 
 import nox
 from nox import Session
@@ -187,7 +188,9 @@ def _prepare_coverage_xml(session: Session, source: Path) -> None:
     session.run(*command)
 
 
-def _upload_to_sonar(session: Session, sonar_token: str, config: Config) -> None:
+def _upload_to_sonar(
+    session: Session, sonar_token: Optional[str], config: Config
+) -> None:
     command = [
         "pysonar",
         "--sonar-token",