gnu: python2: Add upstream security fixes.

This addresses CVE-2018-{1060,1061,14647,1000802}.

* gnu/packages/patches/python2-CVE-2018-1000802.patch,
gnu/packages/patches/python2-CVE-2018-1060.patch,
gnu/packages/patches/python2-CVE-2018-1061.patch,
gnu/packages/patches/python2-CVE-2018-14647.patch: New files.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/python.scm (python-2/fixed): New variable.
(python-2.7)[replacement]: New field.
(python2-minimal): Use PACKAGE/INHERIT.

gnu/packages/patches/python2-CVE-2018-14647.patch

@@ -0,0 +1,61 @@
+Fix CVE-2018-14647:
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-14647
+https://bugs.python.org/issue34623
+
+Taken from upstream:
+https://github.com/python/cpython/commit/18b20bad75b4ff0486940fba4ec680e96e70f3a2
+
+diff --git a/Include/pyexpat.h b/Include/pyexpat.h
+index 5340ef5fa3..3fc5fa54da 100644
+--- a/Include/pyexpat.h
++++ b/Include/pyexpat.h
+@@ -3,7 +3,7 @@
+ 
+ /* note: you must import expat.h before importing this module! */
+ 
+-#define PyExpat_CAPI_MAGIC  "pyexpat.expat_CAPI 1.0"
++#define PyExpat_CAPI_MAGIC  "pyexpat.expat_CAPI 1.1"
+ #define PyExpat_CAPSULE_NAME "pyexpat.expat_CAPI"
+ 
+ struct PyExpat_CAPI 
+@@ -43,6 +43,8 @@ struct PyExpat_CAPI
+         XML_Parser parser, XML_UnknownEncodingHandler handler,
+         void *encodingHandlerData);
+     void (*SetUserData)(XML_Parser parser, void *userData);
++    /* might be none for expat < 2.1.0 */
++    int (*SetHashSalt)(XML_Parser parser, unsigned long hash_salt);
+     /* always add new stuff to the end! */
+ };
+ 
+diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
+index f7f992dd3a..b38e0ab329 100644
+--- a/Modules/_elementtree.c
++++ b/Modules/_elementtree.c
+@@ -2574,6 +2574,11 @@ xmlparser(PyObject* self_, PyObject* args, PyObject* kw)
+         PyErr_NoMemory();
+         return NULL;
+     }
++    /* expat < 2.1.0 has no XML_SetHashSalt() */
++    if (EXPAT(SetHashSalt) != NULL) {
++        EXPAT(SetHashSalt)(self->parser,
++                           (unsigned long)_Py_HashSecret.prefix);
++    }
+ 
+     ALLOC(sizeof(XMLParserObject), "create expatparser");
+ 
+diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
+index 2b4d31293c..1f8c0d70a5 100644
+--- a/Modules/pyexpat.c
++++ b/Modules/pyexpat.c
+@@ -2042,6 +2042,11 @@ MODULE_INITFUNC(void)
+     capi.SetProcessingInstructionHandler = XML_SetProcessingInstructionHandler;
+     capi.SetUnknownEncodingHandler = XML_SetUnknownEncodingHandler;
+     capi.SetUserData = XML_SetUserData;
++#if XML_COMBINED_VERSION >= 20100
++    capi.SetHashSalt = XML_SetHashSalt;
++#else
++    capi.SetHashSalt = NULL;
++#endif
+ 
+     /* export using capsule */
+     capi_object = PyCapsule_New(&capi, PyExpat_CAPSULE_NAME, NULL);