Error 500 due to encoding issues when when attempting to access issues API

https://sentry.gitlap.com/gitlab/gitlabcom/issues/511909/

Encoding::CompatibilityError: incompatible character encodings: ASCII-8BIT and UTF-8
  banzai/renderer/common_mark/html.rb:12:in `block in code_block'
    "<code#{lang_attr}>#{ERB::Util.html_escape(code)}</code>" \
  commonmarker/renderer.rb:74:in `block'
    yield
  banzai/renderer/common_mark/html.rb:6:in `code_block'
    block do
  commonmarker/renderer.rb:40:in `render'
    send(node.type, node)
  commonmarker/renderer/html_renderer.rb:4:in `render'
    super(node)
...
(207 additional frame(s) were not displayed)

Encoding::CompatibilityError: incompatible character encodings: ASCII-8BIT and UTF-8