[3/n] make tufaceous assemble exit with non-zero on failure

Realized while writing tests here that we exit on failure with a zero exit code. That's okay for cleanup but not for the assembly itself.

Reviewers: iliana

Reviewed By: iliana

Pull Request: #19

Author: sunshowers

bin/tests/integration-tests/command_tests.rs

@@ -273,8 +273,7 @@ fn test_assemble_duplicate_artifact() -> Result<()> {
         "invalid-manifests/duplicate-artifact.toml",
     ]);
     cmd.arg(&archive_path);
-    // TODO: this should be failure, not success!
-    cmd.assert().success().stderr(predicate::str::contains(
+    cmd.assert().failure().stderr(predicate::str::contains(
         "a target named gimlet_sp-fake-gimlet-sp-1.0.0.tar.gz \
          already exists in the repository",
     ));

lib/src/assemble/build.rs

@@ -79,17 +79,16 @@ impl OmicronRepoAssembler {
                     "artifacts assembled and archived to `{}`",
                     self.output_path
                 );
+                Ok(())
             }
             Err(error) => {
-                slog::error!(self.log, "assembly failed: {error:?}");
-                slog::info!(
+                slog::error!(
                     self.log,
-                    "failing build directory preserved: `{build_dir}`"
+                    "assembly failed, failing build directory preserved: `{build_dir}`"
                 );
+                Err(error)
             }
         }
-
-        Ok(())
     }
 
     async fn build_impl(&self, build_dir: &Utf8Path) -> Result<()> {