PKIX path building failed

I was gradle'ng on the Raspberry Pi Zero as usual, and during a build, I had the following message: 

sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

What the Fr*nch??!

I spent too much time and sweat trying to find a solution.

If that happens to you, just re-install your JDK!

sudo apt-get update 

sudo apt-get install openjdk-8-jdk-headless

The Raspberry Pi Zero cannot - so far - run a Java version above 8. 

This operation above also re-installs the required certificates. 

And you're back on track.