Fix error reporting on very early errors when the Cython runtime configuration...

Fix error reporting on very early errors when the Cython runtime configuration module is not set up yet.
See #2199.

Cython/Compiler/ModuleNode.py

@@ -707,7 +707,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
         code.putln('static PyObject *%s = NULL;' % env.module_cname)
         code.putln('static PyObject *%s;' % env.module_dict_cname)
         code.putln('static PyObject *%s;' % Naming.builtins_cname)
-        code.putln('static PyObject *%s;' % Naming.cython_runtime_cname)
+        code.putln('static PyObject *%s = NULL;' % Naming.cython_runtime_cname)
         code.putln('static PyObject *%s;' % Naming.empty_tuple)
         code.putln('static PyObject *%s;' % Naming.empty_bytes)
         code.putln('static PyObject *%s;' % Naming.empty_unicode)

Cython/Utility/Exceptions.c

@@ -617,6 +617,12 @@ static int __Pyx_CLineForTraceback(CYTHON_UNUSED PyThreadState *tstate, int c_li
 #if CYTHON_COMPILING_IN_CPYTHON
     PyObject **cython_runtime_dict;
 #endif
+
+    if (unlikely(!${cython_runtime_cname})) {
+        // Very early error where the runtime module is not set up yet.
+        return c_line;
+    }
+
     __Pyx_ErrFetchInState(tstate, &ptype, &pvalue, &ptraceback);
 
 #if CYTHON_COMPILING_IN_CPYTHON