Maven 3.8.1 blocked mirrors

This is not a fix, but a workaround for repositories not on HTTPS yet. Use with caution.

Error

[ERROR] (...) Could not transfer artifact no.whatever:whatever-client:pom:3.1 from/to maven-default-http-blocker (http://0.0.0.0/): Blocked mirror for repositories: [releases (http://unportected.com/nexus/content/repositories/releases, defaul)] -> [Help 1]

Solution

Put this section in your ~/.m2/settings.xml-file, and rerun mvn with -U option. U're done ✅.

<settings xmlns="http://maven.apache.org/SETTINGS/1.2.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.2.0 http://maven.apache.org/xsd/settings-1.2.0.xsd">
  ...
    <mirrors>
        <mirror>
            <id>maven-default-http-blocker</id>
            <mirrorOf>external:dont-match-anything-mate:*</mirrorOf>
            <name>Pseudo repository to mirror external repositories initially using HTTP.</name>
            <url>http://0.0.0.0/</url>
            <blocked>false</blocked>
        </mirror>
    </mirrors>
  ...
</settings>