caucase.test: use system environment to run the caucase test

skip the caucase shell test if no jq was installed
this change was write by Vincent Pelletier

caucase/test.py

@@ -3787,6 +3787,8 @@ _caucase_sh_path = find_executable(
 )
 def _runCaucaseSh(*args):
   command = (_caucase_sh_path, ) + args
+  environ = os.environ.copy()
+  environ['CAUCASE_PYTHON'] = sys.executable
   with open(os.devnull, 'rb') as devnull:
     process = subprocess.Popen(
       command,
@@ -3794,9 +3796,7 @@ def _runCaucaseSh(*args):
       stdout=subprocess.PIPE,
       stderr=subprocess.STDOUT,
       close_fds=True,
-      env={
-        'CAUCASE_PYTHON': sys.executable,
-      },
+      env=environ,
     )
     stdout, _ = process.communicate()
     status = process.wait()