plugin: _execute_commands_in_subprocess: make sure pipes get closed

electrum/plugin.py

@@ -338,12 +338,12 @@ class Plugins(DaemonThread):
         Executes the given commands in a subprocess and asserts that it was successful.
         """
         import subprocess
-        process = subprocess.Popen(
+        with subprocess.Popen(
             commands,
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
-            text=True
-        )
+            text=True,
+        ) as process:
             stdout, stderr = process.communicate()
             if process.returncode != 0:
                 raise Exception(f'error executing command ({process.returncode}): {stderr}')