Issue #15340: Fix importing the random module when /dev/urandom cannot be opened.

This was a regression caused by the hash randomization patch.

Misc/NEWS

@@ -18,6 +18,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #15340: Fix importing the random module when /dev/urandom cannot
+  be opened.  This was a regression caused by the hash randomization patch.
+
 - Issue #15785: Modify window.get_wch() API of the curses module: return
   a character for most keys, and an integer for special keys, instead of
   always returning an integer. So it is now possible to distinguish special

Python/random.c

@@ -165,7 +165,8 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
     Py_END_ALLOW_THREADS
     if (fd < 0)
     {
-        PyErr_SetFromErrnoWithFilename(PyExc_OSError, "/dev/urandom");
+        PyErr_SetString(PyExc_NotImplementedError,
+                        "/dev/urandom (or equivalent) not found");
         return -1;
     }