Android: fix warnings in runner script

Remove f-format prints that uses no placeholders.

Check if logcat_process is initialized before accessing it.

Remove unused import.

Change-Id: I72cc34666460300b3b6b58174b3c7cefac27da7d
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
(cherry picked from commit 2eeb35539c4ab0cf1f4d1d15cb974b4d6b7ff720)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

libexec/qt-android-runner.py

@@ -10,8 +10,6 @@ import time
 import signal
 import argparse
 
-from datetime import datetime
-
 def status(msg):
     print(f"\n-- {msg}")
 
@@ -69,10 +67,10 @@ try:
             serial = line.split('\t')[0]
             devices.append(serial)
     if not devices:
-        die(f"No devices are connected.")
+        die("No devices are connected.")
 
     if args.serial and not args.serial in devices:
-        die(f"No connected devices with the specified serial number.")
+        die("No connected devices with the specified serial number.")
 except Exception as e:
     die(f"Failed to check for running devices, received error: {e}")
 
@@ -170,11 +168,12 @@ def terminate_app(signum, frame):
 signal.signal(signal.SIGINT, terminate_app)
 
 # Show app's logs
+logcat_process = None;
 try:
     format_arg = "-v brief -v color"
     time_arg = f"-T '{start_timestamp}'"
     # escape char and color followed with fatal tag
-    fatal_regex = f"-e $'^\x1b\\[[0-9]*mF/'"
+    fatal_regex = "-e $'^\x1b\\[[0-9]*mF/'"
     pid_regex = f"-e '([ ]*{pid}):'"
     logcat_cmd = f"{adb} shell \"logcat {time_arg} {format_arg} | grep {pid_regex} {fatal_regex}\""
     logcat_process = subprocess.Popen(logcat_cmd, shell=True)
@@ -195,7 +194,8 @@ try:
             status(f"The app \"{package_name}\" has exited")
             break
 finally:
-    logcat_process.terminate()
+    if logcat_process:
+        logcat_process.terminate()
 
 if interrupted:
     try: