`apollo service:check --markdown` options throw error

[vreality64]

Intended outcome:

$ npx apollo service:check --tag develop --markdown

I think markdown output should be in form not error.

---

Apollo Service Check

🔄 Validated your local schema against schema tag develop on service ....
🔢 Compared 0 schema change against 0 operations seen over the last 30 days.
✅ Found no breaking changes.

🔗 View your service check details.

---

Actual outcome:

Error

$ npx apollo service:check --tag develop --markdown
Error: checkSchemaResult.diffToPrevious.validationConfig missing
    at formatMarkdown (~/.../service/check.js:54:15)
    at ServiceCheck.run (~/.../service/check.js:208:29)
    at <anonymous>

How to reproduce the issue:

Pre condition: no changes between local and engine schema. if schema changes, it works. It's normal case as CI integration command service:check

$ npx apollo service:check --markdown

Versions

$ npx apollo -v

apollo/2.9.0 darwin-x64 node-v8.11.3

[trevor-scheer]

@justinanastos, would you mind taking a look at this? Seems like a valid bug.

[parshap]

I'm running into this same issue as well when apollo service:check runs in CI when there is no schema diff.