Fix SF #561858 Assertion with very long lists

if co_stacksize was > 32767 (the maximum value
which can be stored in 16 bits (signed)),
the PyCodeObject would be written wrong.
So on the second import (reading the .pyc)
would cause a crash.

Since we can't change the PYC magic, we
go on (silently), but don't write the file.
This means everything will work, but
a .pyc will not be written and the file will need
to be parsed on each import.

I will backport.

Python/import.c

@@ -19,6 +19,9 @@
 #include <fcntl.h>
 #endif
 
+/* check if the int_value can't be written in 15 bits (signed) */
+#define CANT_WRITE(int_value)	(int_value > 32767)
+
 extern time_t PyOS_GetLastModificationTime(char *, FILE *);
 						/* In getmtime.c */
 
@@ -687,6 +690,18 @@ write_compiled_module(PyCodeObject *co, char *cpathname, long mtime)
 {
 	FILE *fp;
 
+	if (CANT_WRITE(co->co_argcount) ||
+	    CANT_WRITE(co->co_nlocals) ||
+	    CANT_WRITE(co->co_stacksize) ||
+	    CANT_WRITE(co->co_flags) ||
+	    CANT_WRITE(co->co_firstlineno)) {
+		if (Py_VerboseFlag)
+			PySys_WriteStderr(
+				"# code too large: can't write %s\n",
+				cpathname);
+		return;
+	}
+
 	fp = open_exclusive(cpathname);
 	if (fp == NULL) {
 		if (Py_VerboseFlag)