mavsdk_tests: better process management

We now error if px4 or gzserver are already running on startup, and we
also make sure to terminate what we started if interrupted.

test/mavsdk_tests/mavsdk_test_runner.py

@@ -1,8 +1,10 @@
 #!/usr/bin/env python3
 
 import argparse
+import atexit
 import datetime
 import os
+import psutil
 import subprocess
 import sys
 
@@ -51,13 +53,17 @@ def start(self, config):
             stdout=f, stderr=f
         )
 
+        atexit.register(self.stop)
+
     def wait(self, timeout_s):
         try:
             return self.process.wait(timeout=timeout_s)
         except subprocess.TimeoutExpired:
             self.stop()
 
     def stop(self):
+        atexit.unregister(self.stop)
+
         returncode = self.process.poll()
         if returncode is not None:
             return returncode
@@ -117,13 +123,31 @@ def __init__(self, workspace_dir, log_dir, config):
         self.log_prefix = "test_runner"
 
 
+def is_everything_ready():
+    result = True
+    for proc in psutil.process_iter(attrs=['name']):
+        if proc.info['name'] == 'gzserver':
+            print("gzserver process already running\n"
+                  "run `killall gzserver` and try again")
+            result = False
+        elif proc.info['name'] == 'px4':
+            print("px4 process already running\n"
+                  "run `killall px4` and try again")
+            result = False
+
+    return result
+
+
 def main():
 
     parser = argparse.ArgumentParser()
     parser.add_argument("--log-dir",
                         help="Directory for log files, stdout if not provided")
     args = parser.parse_args()
 
+    if not is_everything_ready():
+        return
+
     for group in test_matrix:
         print("Running test group for '{}' with filter '{}'"
               .format(group['model'], group['test_filter']))