I've been building my own snap and installing it successfully for a while now, but just today, every time I build my snap file, when I try to install it, I get...
error: cannot find signatures with metadata for snap "mysnap_1.0_amd64.snap"
I am at a complete loss. What does this mean? How do I fix it? I can't think of what I've done to cause this to start happening.
Yeah this is a terribly unhelpful error, I have no idea why they haven't fixed it. It relates to "assertions" in snapd. In this case, that is the verification that the snap comes from a trusted party. Since you're installing a local snap, you have no assertions for it, and snapd doesn't trust it. Think of it a bit like sideloading Android apps, if you've ever done that.
Regardless, you can get past this during your testing with the also-terribly-named --dangerous flag:
$ sudo snap install --dangerous <snap>
note: there was some churn on this flag; in earlier releases it was --force-dangerous.
