I think this can be one line.

I am actually using the path variable later on in the loop on line 93, to access the correct dictionary key. Unfortunately, I do not think I can make this one line without using a ternary operator, which is best avoided.
Thank you for the review!

There should be an empty line before this.

switch with checkstyle for alphabetical order

wrap with parenthesis instead of line break character to be more consistent with rest of codebase

This should have a try/except to catch any issues executing the program.
Also, how about just calling this lines? I think it communicates things better.

Rather than range, we should use enumerate:

num_lines = len(clippy_output)

for i, line in enumerate(clippy_output):
    if i + 1 >= num_lines:
        break

    next_line = clippy_output[i + 1].lstrip()

    if (line.startswith(prefixes) and
        next_line.startswith('--> ')):
        ...


Note the addition of the first check in that loop. As-is, your code could end up crashing at a boundary.
Also, pulling out next_line, so we don't have to pull it out and lstrip it again inside the block.

Let's use filename instead of file_. It communicates it better and avoids the conflict.
Also, we should never override _, as that's used in our code (or really anything using gettext localization) as an alias for ugettext/ugettext_lazy, and will inevitably result in that being overridden.
One final note: We should have a try/except here, because if we get a string here that has too many or too few items, we'll crash.

Can you update this to use single quotes, and alphabetize keys?

The int(line_num) will crash if line_num isn't what we expect, so it should go within any try/except.

This should have a try/except.

Some of the same comments as above:

enumerate (saves a lookup each iteration)
Don't assume a split is successful
Don't override _

No need for parens around test_name.

The official terminology seems to be "Cargo commands"

I checked the code base and looks like the style for logger.exception is logger.exception('some string: %s',e). Maybe change the % to a comma to make it consistent?

Ship It!