Lock answers file.

subiquity/cmd/tui.py

@@ -17,6 +17,7 @@
 import argparse
 import logging
 import os
+import fcntl
 import signal
 import sys
 
@@ -126,6 +127,15 @@ def main():
         logger.debug("Autoloading answers from %s", AUTO_ANSWERS_FILE)
         opts.answers = AUTO_ANSWERS_FILE
 
+    if opts.answers:
+        opts.answers = open(opts.answers)
+        try:
+            fcntl.flock(opts.answers, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except OSError:
+            logger.exception('Failed to lock auto answers file, proceding without it.')
+            opts.answers.close()
+            opts.answers = None
+
     ui = SubiquityUI()
 
     try:

subiquitycore/core.py

@@ -263,7 +263,7 @@ class Application:
 
         answers = {}
         if opts.answers is not None:
-            answers = yaml.safe_load(open(opts.answers).read())
+            answers = yaml.safe_load(opts.answers.read())
             log.debug("Loaded answers %s", answers)
             if not opts.dry_run:
                 open('/run/casper-no-prompt', 'w').close()