Spams lots of bogus "type/symbol/whatever not found" errors

[argv-minus-one]

When compiling a Scala mojo, a bunch of bogus error messages are printed concerning missing classes and whatnot. For instance:

<some source file>:3: error: object MojoExecutionException is not a member of package org.apache.maven.plugin
import org.apache.maven.plugin.{MojoExecutionException, MojoFailureException, AbstractMojo}
       ^

This doesn't fail the build and doesn't seem to have any harmful effect beyond the annoyance and confusion of seeing these messages, however.