I realise this annoying thing too since latest m2e-android plugin upgrade (version 0.4.2), it happens in both new project creation and existing project import (if you don't use src/test/java).
It looks like m2e-android (or perhaps m2e) now always trying to add src/test/java as a source folder, regardless of whether it is actually existed in your project directory, in the .classpath file:
<classpathentry kind="src" output="bin/classes" path="src/test/java">
<attributes>
<attribute name="maven.pomderived" value="true"/>
</attributes>
</classpathentry>
As it is already added in the project metadata file, so if you trying to add the source folder via Eclipse, Eclipse will complain that the classpathentry is already exist:
There are several ways to fix it, the easiest is manually create src/test/java directory in the file system, then refresh your project by press F5 and run Maven -> Update Project (Right click project, choose Maven -> Update Project...), this should fix the missing required source folder: 'src/test/java' error.