Add retry.py.

retry.py

@@ -0,0 +1,57 @@
+import argparse
+import subprocess
+import sys
+import time
+
+class NoMoreRetries(Exception):
+    pass
+
+def normalize_limit(limit):
+    if limit is not None:
+        limit = int(limit)
+        if limit < 1:
+            raise ValueError('Limit must be >= 1, or None.')
+    return limit
+
+def normalize_sleepy(sleepy):
+    if sleepy is not None:
+        sleepy = float(sleepy)
+        if sleepy <= 0:
+            raise ValueError('Sleep must be > 0, or None.')
+    return sleepy
+
+def retry(command, limit, sleepy):
+    limit = normalize_limit(limit)
+    sleepy = normalize_sleepy(sleepy)
+    status = 1
+    while limit is None or limit > 0:
+        status = subprocess.run(command, shell=True).returncode
+        if status == 0:
+            return
+        print(f'{command} failed with status {status}.')
+        if limit is not None:
+            limit -= 1
+        if sleepy is not None:
+            time.sleep(sleepy)
+    raise NoMoreRetries()
+
+def retry_argparse(args):
+    return retry(
+        command=args.command,
+        limit=args.limit,
+        sleepy=args.sleepy,
+    )
+
+def main(argv):
+    parser = argparse.ArgumentParser(description=__doc__)
+
+    parser.add_argument('command', nargs='+')
+    parser.add_argument('--limit', dest='limit', type=int, default=None)
+    parser.add_argument('--sleep', dest='sleepy', type=float, default=None)
+    parser.set_defaults(func=retry_argparse)
+
+    args = parser.parse_args(argv)
+    return args.func(args)
+
+if __name__ == '__main__':
+    raise SystemExit(main(sys.argv[1:]))