Using `python3` as the language of a multiline codeblock results in an error

[Seelengrab]

The codeblock:

    ```python3
 
    foo
    ```

The error:

→ Initial full pass...
┌ Franklin Warning: in <index.md>
│ Encountered an issue processing 'index.md' in <article>
│ Verify, then re-start the Franklin server.
│ The error is displayed below:
│ ErrorException("type Nothing has no field captures")
└
ERROR: type Nothing has no field captures
Stacktrace:
  [1] getproperty(x::Nothing, f::Symbol)
    @ Base ./Base.jl:37
  [2] parse_fenced_block(ss::SubString{String}, scut::Bool; shortcut::Bool, repl::Bool, shell::Bool, pkg::Bool, help::Bool)
    @ Franklin ~/.julia/packages/Franklin/R3VpM/src/eval/codeblock.jl:29
[...]

I've omitted the rest of the stacktrace, since the issue seems to be located in that function. I think the regex chosen here (CODE_3_PAT) just doesn't take the 3 into account.

[tlienart]

Thanks @Seelengrab I can adjust the regex; note: if you just use python is the syntax highlighting incorrect?

[Seelengrab]

I'm almost positive that it's correct, but I must admit, once it looked half-way decent I didn't actually check 🤔 Here's the case I was looking at, which seems to render correctly:

The HTML source code also only says python, so I guess it depends on what highlight.js does with that.

[Seelengrab]

I've encountered the same problem when using c++