Pug templates no longer compile with an initial indent

[arnaugiralt]

Version

2.7.1

Reproduction link

https://github.com/arnaugiralt/vue-2.7.1-pug-indent-error

Steps to reproduce

• Clone repo
• npm install
• npm run start

What is expected?

The template should compile

What is actually happening?

Module build failed (from ./node_modules/pug-plain-loader/index.js):
Error: /src/App.vue:2:1
    1| 
  > 2|   #foo
-------^
    3|     h1 Vue 2.7.1 Pug compiler error
    4|     p This template is indented and it breaks during compilation
    5|     p If the indent is removed, everything works just fine

unexpected token "indent"

---

This happened before, in 2.5.18 (see issue #9169).