tensorflow: Backport upstream as bazel build failing for current

temporary/tf-gast.nix

@@ -0,0 +1,16 @@
+{ stdenv, fetchPypi, buildPythonPackage, astunparse }:
+
+buildPythonPackage rec {
+  pname = "gast";
+  version =  "0.2.0";
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "0c296xm1vz9x4w4inmdl0k8mnc0i9arw94si2i7pglpc461r0s3h";
+  };
+  checkInputs = [ astunparse ] ;
+  meta = with stdenv.lib; {
+    description = "GAST provides a compatibility layer between the AST of various Python versions, as produced by ast.parse from the standard ast module.";
+    license = licenses.bsd3;
+    maintainers = with maintainers; [ jyp ];
+  };
+}