switch to extracting json substring using re.

tests/gnmi/test_gnoi_system.py

@@ -4,6 +4,7 @@
 
 from .helper import gnoi_request
 from tests.common.helpers.assertions import pytest_assert
+import re
 
 pytestmark = [
     pytest.mark.topology('any')
@@ -25,11 +26,26 @@ def test_gnoi_system_time(duthosts, rand_one_dut_hostname, localhost):
     ret, msg = gnoi_request(duthost, localhost, "Time", "")
     logging.info("System.Time API returned: {}".format(msg))
     pytest_assert(ret == 0, "System.Time API unexpectedly reported failure")
-    try:
-        # Message should looks like this: System Time\n{"time":1735921221909617549}
-        # Extract JSON part from the message
-        json_part = msg.split('\n', 1)[1]
-        msg_json = json.loads(json_part)
-        pytest_assert("time" in msg_json, "System.Time API did not return time")
-    except (json.JSONDecodeError, IndexError):
-        pytest.fail("System.Time API did not return valid JSON")
+    # Message should contain a json substring like this {"time":1735921221909617549}
+    # Extract JSON part from the message
+    msg_json = extract_first_json_substring(msg)
+    logging.info("Extracted JSON: {}".format(msg_json))
+    pytest_assert("time" in msg_json, "System.Time API did not return time")
+
+
+def extract_first_json_substring(s):
+    """
+    Extract the first JSON substring from a given string.
+
+    :param s: The input string containing JSON substring.
+    :return: The first JSON substring if found, otherwise None.
+    """
+
+    json_pattern = re.compile(r'\{.*?\}')
+    match = json_pattern.search(s)
+    if match:
+        try:
+            return json.loads(match.group())
+        except json.JSONDecodeError:
+            return None
+    return None