refactor: improve pep8 compliance

This changeset fixes PEP8 issues, minus `E501 line too long (80 > 79 characters)`, as that should be more of a guideline than a strict rule, and harder to follow without silly refactoring.

Also removed two unused exception variables.

image/bin/my_init

@@ -1,5 +1,14 @@
 #!/usr/bin/python3 -u
-import os, os.path, sys, stat, signal, errno, argparse, time, json, re
+import argparse
+import errno
+import json
+import os
+import os.path
+import re
+import signal
+import stat
+import sys
+import time
 
 KILL_PROCESS_TIMEOUT = int(os.environ.get('KILL_PROCESS_TIMEOUT', 5))
 KILL_ALL_PROCESSES_TIMEOUT = int(os.environ.get('KILL_ALL_PROCESSES_TIMEOUT', 5))
@@ -15,33 +24,43 @@ log_level = None
 
 terminated_child_processes = {}
 
+_find_unsafe = re.compile(r'[^\w@%+=:,./-]').search
+
+
 class AlarmException(Exception):
     pass
 
+
 def error(message):
     if log_level >= LOG_LEVEL_ERROR:
         sys.stderr.write("*** %s\n" % message)
 
+
 def warn(message):
     if log_level >= LOG_LEVEL_WARN:
         sys.stderr.write("*** %s\n" % message)
 
+
 def info(message):
     if log_level >= LOG_LEVEL_INFO:
         sys.stderr.write("*** %s\n" % message)
 
+
 def debug(message):
     if log_level >= LOG_LEVEL_DEBUG:
         sys.stderr.write("*** %s\n" % message)
 
+
 def ignore_signals_and_raise_keyboard_interrupt(signame):
     signal.signal(signal.SIGTERM, signal.SIG_IGN)
     signal.signal(signal.SIGINT, signal.SIG_IGN)
     raise KeyboardInterrupt(signame)
 
+
 def raise_alarm_exception():
     raise AlarmException('Alarm')
 
+
 def listdir(path):
     try:
         result = os.stat(path)
@@ -52,12 +71,14 @@ def listdir(path):
     else:
         return []
 
+
 def is_exe(path):
     try:
         return os.path.isfile(path) and os.access(path, os.X_OK)
     except OSError:
         return False
 
+
 def import_envvars(clear_existing_environment=True, override_existing_environment=True):
     if not os.path.exists("/etc/container_environment"):
         return
@@ -73,9 +94,10 @@ def import_envvars(clear_existing_environment = True, override_existing_environm
     if clear_existing_environment:
         os.environ.clear()
     for name, value in new_env.items():
-		if override_existing_environment or not name in os.environ:
+        if override_existing_environment or name not in os.environ:
             os.environ[name] = value
 
+
 def export_envvars(to_dir=True):
     if not os.path.exists("/etc/container_environment"):
         return
@@ -92,7 +114,6 @@ def export_envvars(to_dir = True):
     with open("/etc/container_environment.json", "w") as f:
         f.write(json.dumps(dict(os.environ)))
 
-_find_unsafe = re.compile(r'[^\w@%+=:,./-]').search
 
 def shquote(s):
     """Return a shell-escaped version of the string *s*."""
@@ -105,9 +126,11 @@ def shquote(s):
     # the string $'b is then quoted as '$'"'"'b'
     return "'" + s.replace("'", "'\"'\"'") + "'"
 
+
 def sanitize_shenvname(s):
     return re.sub(SHENV_NAME_WHITELIST_REGEX, "_", s)
 
+
 # Waits for the child process with the given PID, while at the same time
 # reaping any other child processes that have exited (e.g. adopted child
 # processes that have terminated).
@@ -143,6 +166,7 @@ def waitpid_reap_other_children(pid):
                 raise
     return status
 
+
 def stop_child_process(name, pid, signo=signal.SIGTERM, time_limit=KILL_PROCESS_TIMEOUT):
     info("Shutting down %s (PID %d)..." % (name, pid))
     try:
@@ -168,13 +192,14 @@ def stop_child_process(name, pid, signo = signal.SIGTERM, time_limit = KILL_PROC
     finally:
         signal.alarm(0)
 
+
 def run_command_killable(*argv):
     filename = argv[0]
     status = None
     pid = os.spawnvp(os.P_NOWAIT, filename, argv)
     try:
         status = waitpid_reap_other_children(pid)
-	except BaseException as s:
+    except BaseException:
         warn("An error occurred. Aborting.")
         stop_child_process(filename, pid)
         raise
@@ -185,11 +210,13 @@ def run_command_killable(*argv):
             error("%s failed with status %d\n" % (filename, os.WEXITSTATUS(status)))
         sys.exit(1)
 
+
 def run_command_killable_and_import_envvars(*argv):
     run_command_killable(*argv)
     import_envvars()
     export_envvars(False)
 
+
 def kill_all_processes(time_limit):
     info("Killing all processes...")
     try:
@@ -217,6 +244,7 @@ def kill_all_processes(time_limit):
     finally:
         signal.alarm(0)
 
+
 def run_startup_files():
     # Run /etc/my_init.d/*
     for name in listdir("/etc/my_init.d"):
@@ -230,13 +258,18 @@ def run_startup_files():
         info("Running /etc/rc.local...")
         run_command_killable_and_import_envvars("/etc/rc.local")
 
+
 def start_runit():
     info("Booting runit daemon...")
-	pid = os.spawnl(os.P_NOWAIT, "/usr/bin/runsvdir", "/usr/bin/runsvdir",
+    pid = os.spawnl(os.P_NOWAIT,
-		"-P", "/etc/service")
+                    "/usr/bin/runsvdir",
+                    "/usr/bin/runsvdir",
+                    "-P",
+                    "/etc/service")
     info("Runit started as PID %d" % pid)
     return pid
 
+
 def wait_for_runit_or_interrupt(pid):
     try:
         status = waitpid_reap_other_children(pid)
@@ -244,11 +277,13 @@ def wait_for_runit_or_interrupt(pid):
     except KeyboardInterrupt:
         return (False, None)
 
+
 def shutdown_runit_services(quiet=False):
     if not quiet:
         debug("Begin shutting down runit services...")
     os.system("/usr/bin/sv -w %d down /etc/service/* > /dev/null" % KILL_PROCESS_TIMEOUT)
 
+
 def wait_for_runit_services():
     debug("Waiting for runit services to exit...")
     done = False
@@ -263,10 +298,12 @@ def wait_for_runit_services():
             # services.
             shutdown_runit_services(True)
 
+
 def install_insecure_key():
     info("Installing insecure SSH key for user root")
     run_command_killable("/usr/sbin/enable_insecure_key")
 
+
 def main(args):
     import_envvars(False, False)
     export_envvars()
@@ -295,7 +332,9 @@ def main(args):
                     info("Runit exited with status %d" % exit_status)
         else:
             info("Running %s..." % " ".join(args.main_command))
-			pid = os.spawnvp(os.P_NOWAIT, args.main_command[0], args.main_command)
+            pid = os.spawnvp(os.P_NOWAIT,
+                             args.main_command[0],
+                             args.main_command)
             try:
                 exit_code = waitpid_reap_other_children(pid)
                 if exit_code is None:
@@ -307,7 +346,7 @@ def main(args):
             except KeyboardInterrupt:
                 stop_child_process(args.main_command[0], pid)
                 raise
-			except BaseException as s:
+            except BaseException:
                 warn("An error occurred. Aborting.")
                 stop_child_process(args.main_command[0], pid)
                 raise
@@ -319,24 +358,49 @@ def main(args):
                 stop_child_process("runit daemon", runit_pid)
             wait_for_runit_services()
 
+
 # Parse options.
 parser = argparse.ArgumentParser(description='Initialize the system.')
-parser.add_argument('main_command', metavar = 'MAIN_COMMAND', type = str, nargs = '*',
+parser.add_argument(
+    'main_command',
+    metavar='MAIN_COMMAND',
+    type=str,
+    nargs='*',
     help='The main command to run. (default: runit)')
-parser.add_argument('--enable-insecure-key', dest = 'enable_insecure_key',
+parser.add_argument(
-	action = 'store_const', const = True, default = False,
+    '--enable-insecure-key',
+    dest='enable_insecure_key',
+    action='store_const',
+    const=True,
+    default=False,
     help='Install the insecure SSH key')
-parser.add_argument('--skip-startup-files', dest = 'skip_startup_files',
+parser.add_argument(
-	action = 'store_const', const = True, default = False,
+    '--skip-startup-files',
+    dest='skip_startup_files',
+    action='store_const',
+    const=True,
+    default=False,
     help='Skip running /etc/my_init.d/* and /etc/rc.local')
-parser.add_argument('--skip-runit', dest = 'skip_runit',
+parser.add_argument(
-	action = 'store_const', const = True, default = False,
+    '--skip-runit',
+    dest='skip_runit',
+    action='store_const',
+    const=True,
+    default=False,
     help='Do not run runit services')
-parser.add_argument('--no-kill-all-on-exit', dest = 'kill_all_on_exit',
+parser.add_argument(
-	action = 'store_const', const = False, default = True,
+    '--no-kill-all-on-exit',
-	help = 'Don\'t kill all processes on the system upon exiting')
+    dest='kill_all_on_exit',
-parser.add_argument('--quiet', dest = 'log_level',
+    action='store_const',
-	action = 'store_const', const = LOG_LEVEL_WARN, default = LOG_LEVEL_INFO,
+    const=False,
+    default=True,
+    help='Do not kill all processes on the system upon exiting')
+parser.add_argument(
+    '--quiet',
+    dest='log_level',
+    action='store_const',
+    const=LOG_LEVEL_WARN,
+    default=LOG_LEVEL_INFO,
     help='Only print warnings and errors')
 args = parser.parse_args()
 log_level = args.log_level
@@ -346,9 +410,12 @@ if args.skip_runit and len(args.main_command) == 0:
     sys.exit(1)
 
 # Run main function.
-signal.signal(signal.SIGTERM, lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGTERM'))
+signal.signal(signal.SIGTERM,
-signal.signal(signal.SIGINT, lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGINT'))
+              lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGTERM'))
-signal.signal(signal.SIGALRM, lambda signum, frame: raise_alarm_exception())
+signal.signal(signal.SIGINT,
+              lambda signum, frame: ignore_signals_and_raise_keyboard_interrupt('SIGINT'))
+signal.signal(signal.SIGALRM,
+              lambda signum, frame: raise_alarm_exception())
 try:
     main(args)
 except KeyboardInterrupt: