Hardening of Temporary-Directory Usage

Defends against certain forms of local privilege escalation, i.e.
understood to be defense in depth rather than a security issue given
the recommended ways of deploying (docker container or in a single-use
single-server)

Fix #174

See https://github.com/python/cpython/pull/23901

bsmain/future_python.py

@@ -0,0 +1,52 @@
+# A backport of a not-yet-released version of Python's os.makedirs
+#
+# License: Python Software Foundation License
+#
+# From:
+# https://github.com/python/cpython/pull/23901 as per
+# https://github.com/python/cpython/pull/23901/commits/128ff8b46696c26e2cea5609cf9840b9425dcccf
+#
+# Note on stability: os.makedirs has not seen any changes after Python 3.7 up to
+# 3.13 (3.14 is in pre-release, so unlikely to see changes). This means that the
+# current code can be used as a "extra feature" drop in for at least those versions.
+
+from os import path, mkdir, curdir
+
+
+def makedirs(name, mode=0o777, exist_ok=False, *, recursive_mode=False):
+    """makedirs(name [, mode=0o777][, exist_ok=False][, recursive_mode=False])
+
+    Super-mkdir; create a leaf directory and all intermediate ones.  Works like
+    mkdir, except that any intermediate path segment (not just the rightmost)
+    will be created if it does not exist. If the target directory already
+    exists, raise an OSError if exist_ok is False. Otherwise no exception is
+    raised.  If recursive_mode is True, the mode argument will affect the file
+    permission bits of any newly-created, intermediate-level directories.  This
+    is recursive.
+
+    """
+    head, tail = path.split(name)
+    if not tail:
+        head, tail = path.split(head)
+    if head and tail and not path.exists(head):
+        try:
+            if recursive_mode:
+                makedirs(head, mode=mode, exist_ok=exist_ok,
+                         recursive_mode=True)
+            else:
+                makedirs(head, exist_ok=exist_ok)
+        except FileExistsError:
+            # Defeats race condition when another thread created the path
+            pass
+        cdir = curdir
+        if isinstance(tail, bytes):
+            cdir = bytes(curdir, 'ASCII')
+        if tail == cdir:           # xxx/newdir/. exists if xxx/newdir exists
+            return
+    try:
+        mkdir(name, mode)
+    except OSError:
+        # Cannot rely on checking for EEXIST, since the operating system
+        # could give priority to other errors like EACCES or EROFS
+        if not exist_ok or not path.isdir(name):
+            raise