update runt to use python3

Author: UnsignedByte

runt.toml

@@ -124,7 +124,7 @@ name = "blas"
 paths = ["apps/blas/*/test.fil"]
 expect_dir = "apps/blas/"
 cmd = """
-python apps/blas/util.py -r -n 5 -w 4 -k {} && \
+python3 apps/blas/util.py -r -n 5 -w 4 -k {} && \
 dir=$(dirname {}) && \
 rm $dir/test.expect $dir/test.fil.data $dir/test.fil.out
 """