Python3.4 support. README.md update

tests/README.md

@@ -15,6 +15,13 @@ C testing framework.
 There's a test runner script `test_runner.py` written in Python3 that runs
 test cases on ESP8266 connected to a host.
 
+### Requirements and dependencies
+
+* Python3 version > 3.4 `sudo apt-get install python3 python3-pip`
+* pyserial `sudo pip3 install pyserial`
+* ESP8266 board with reset to boot mode support
+* Two ESP8266 for dual mode test cases
+
 Test runner is heavily relying on device reset using DTR and RTS signals.
 Popular ESP8266 boards such as **NodeMcu** and **Wemos D1** support device
 reset into flash mode.

tests/test_runner.py

@@ -291,8 +291,8 @@ def flash_image(serial_port):
     verbose_print("Building and flashing test image to %s..." % serial_port)
     try:
         stdout = sys.stdout if verbose else None
-        subprocess.run(["make", "flash"], check=True, cwd=get_testdir(),
-                       stdout=stdout, stderr=subprocess.STDOUT, env=env)
+        subprocess.check_call(["make", "flash"], cwd=get_testdir(),
+                              stdout=stdout, stderr=subprocess.STDOUT, env=env)
     except subprocess.CalledProcessError as e:
         raise TestRunnerError("'make flash EPPORT=%s' failed with exit code %d" %
                               (serial_port, e.returncode))