Is there a way to ask TravisCI to ignore specifc parts of codebase?

What do you mean? TravisCI just runs your Spryker tools. Most of the tools (e.g.:

console code:sniff:style

) allow to pass the directory that should be checked into (e.g.:

console code:sniff:style src/Pyz/Zed/

to only check code style for Zed). So you could run the tools only on the necessary directories. But in almost any case excluding parts is the last option. Better fix what the tool is showing to avoid pilling up technical debt and code smells as the reality has proven that those are never be solved once they are ignored.