E0070 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0070.rs

Error E0070 needs a span_label, updating it from:

error[E0070]: invalid left-hand side expression
  --> src/test/compile-fail/E0070.rs:18:5
   |
18 |     some_other_func() = 4; //~ ERROR E0070
   |     ^^^^^^^^^^^^^^^^^^^^^

To:

error[E0070]: invalid left-hand side expression
  --> src/test/compile-fail/E0070.rs:18:5
   |
18 |     some_other_func() = 4; //~ ERROR E0070
   |     ^^^^^^^^^^^^^^^^^^^^^ left-hand of expression not valid

[clementmiao]

I would like to take this issue. First time compiler hacker :)

[sophiajt]

@clementmiao - I've updated the list to reflect you having E0067 and E0070. Have fun! If you get stuck, you can look through the accepted PRs to see how other people did their fixes.