Add bats test for python-build

plugins/python-build/test/fetch.bats

@@ -0,0 +1,14 @@
+#!/usr/bin/env bats
+
+load test_helper
+export PYTHON_BUILD_SKIP_MIRROR=1
+export PYTHON_BUILD_CACHE_PATH=
+
+@test "failed download displays error message" {
+  stub curl false
+
+  install_fixture definitions/without-checksum
+  assert_failure
+  assert_output_contains "> http://example.com/packages/package-1.0.0.tar.gz"
+  assert_output_contains "error: failed to download package-1.0.0.tar.gz"
+}