old_contents: #!/usr/bin/env python
  
  from __future__ import print_function
  
  import sys
  import glob
  import subprocess
  import sys
  import logging
  import dateutil.parser
  import pytz
  from datetime import datetime, timedelta
  if False:
      from typing import Dict, List
  
  logging.basicConfig(format="%(asctime)s %(levelname)s: %(message)s")
  logger = logging.getLogger(__name__)
  
  def run(args, dry_run=False):
      # type: (List[str], bool) -> str
      if dry_run:
          print("Would have run: " + " ".join(args))
          return ""
  
      p = subprocess.Popen(args, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE)
      stdout, stderr = p.communicate()
      if p.returncode:
          logger.error("Could not invoke %s\nstdout: %s\nstderror: %s"
                       % (args[0], stdout, stderr))
          sys.exit(1)
      return stdout
  
  # Only run if we're the master
  if run(['psql', '-t', '-c', 'select pg_is_in_recovery()']).strip() != 'f':
      sys.exit(0)
  
  pg_data_paths = glob.glob('/var/lib/postgresql/*/main')
  if len(pg_data_paths) != 1:
      print("Postgres installation is not unique: %s" % (pg_data_paths,))
      sys.exit(1)
  pg_data_path = pg_data_paths[0]
  run(['env-wal-e', 'backup-push', pg_data_path])
  
  now = datetime.now(tz=pytz.utc)
  with open('/var/lib/nagios_state/last_postgres_backup', 'w') as f:
      f.write(now.isoformat())
      f.write("\n")
  
  backups = {} # type: Dict[datetime, str]
  lines = run(['env-wal-e', 'backup-list']).split("\n")
  for line in lines[1:]:
      if line:
          backup_name, date_str, _, _ = line.split()
          backups[dateutil.parser.parse(date_str)] = backup_name
  
  one_month_ago = now - timedelta(days=30)
  for date in sorted(backups.keys(), reverse=True):
      if date < one_month_ago:
          run(['env-wal-e', 'delete', '--confirm', 'before', backups[date]])
          # Because we're going from most recent to least recent, we
          # only have to do one delete operation
          break
  
new_contents: #!/usr/bin/env python
  
  from __future__ import print_function
  
  import sys
  import glob
  import subprocess
  import sys
  import logging
  import dateutil.parser
  import pytz
  from datetime import datetime, timedelta
  if False:
      from typing import Dict, List
  
  logging.basicConfig(format="%(asctime)s %(levelname)s: %(message)s")
  logger = logging.getLogger(__name__)
  
  def run(args, dry_run=False):
      # type: (List[str], bool) -> str
      if dry_run:
          print("Would have run: " + " ".join(args))
          return ""
  
      p = subprocess.Popen(args, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE)
      stdout, stderr = p.communicate()
      if p.returncode:
          logger.error("Could not invoke %s\nstdout: %s\nstderror: %s"
                       % (args[0], stdout, stderr))
          sys.exit(1)
      return stdout
  
  # Only run if we're the master
  if run(['psql', '-t', '-c', 'select pg_is_in_recovery()']).strip() != 'f':
      sys.exit(0)
  
  pg_data_paths = glob.glob('/var/lib/postgresql/*/main')
  if len(pg_data_paths) != 1:
      print("Postgres installation is not unique: %s" % (pg_data_paths,))
      sys.exit(1)
  pg_data_path = pg_data_paths[0]
  run(['env-wal-e', 'backup-push', pg_data_path])
  
  now = datetime.now(tz=pytz.utc)
  with open('/var/lib/nagios_state/last_postgres_backup', 'w') as f:
      f.write(now.isoformat())
      f.write("\n")
  
  backups = {}  # type: Dict[datetime, str]
  lines = run(['env-wal-e', 'backup-list']).split("\n")
  for line in lines[1:]:
      if line:
          backup_name, date_str, _, _ = line.split()
          backups[dateutil.parser.parse(date_str)] = backup_name
  
  one_month_ago = now - timedelta(days=30)
  for date in sorted(backups.keys(), reverse=True):
      if date < one_month_ago:
          run(['env-wal-e', 'delete', '--confirm', 'before', backups[date]])
          # Because we're going from most recent to least recent, we
          # only have to do one delete operation
          break
  
subject: Add compliance with rule E261 to pg_backup_and_purge.py.