pyln-testing: Fix BitcoinD fd leak

Author: s373nZ

CHANGELOG.md

@@ -3,6 +3,11 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [Unreleased]
+
+### Added
+
+- pyln-testing: Fix FD leaks in BitcoinD. ([#7130])
 
 ## [24.08] - 2024-08-28: "Steel Backed-up Channels"
 

contrib/pyln-testing/pyln/testing/fixtures.py

@@ -164,6 +164,8 @@ def bitcoind(directory, teardown_checks):
         bitcoind.proc.kill()
     bitcoind.proc.wait()
 
+    bitcoind.cleanup_files()
+
 
 class TeardownErrors(object):
     def __init__(self):

contrib/pyln-testing/pyln/testing/utils.py

@@ -256,6 +256,14 @@ def kill(self):
         self.proc.kill()
         self.proc.wait()
 
+    def cleanup_files(self):
+        """Ensure files are closed."""
+        for f in ["stdout_write", "stderr_write", "stdout_read", "stderr_read"]:
+            try:
+                getattr(self, f).close()
+            except Exception:
+                pass
+
     def logs_catchup(self):
         """Save the latest stdout / stderr contents; return true if we got anything.
         """