docs: protected void validateProjectFile() 
              throws MojoExecutionException
      {
          if ( projectFile != null
                  && projectFile.exists()
                  && projectFile.isFile() )
          {
              getLog().debug( "Project file validated at " + projectFile );
  
              boolean solutionFile = projectFile.getName().toLowerCase().endsWith( "." + SOLUTION_EXTENSION ); 
              if ( ( MSBuildPackaging.isSolution( mavenProject.getPackaging() ) && ! solutionFile )
                      || ( ! MSBuildPackaging.isSolution( mavenProject.getPackaging() ) && solutionFile ) )
              {
                  // Solution packaging defined but the projectFile is not a .sln
                  String msg = "Packaging doesn't match project file type. "
                          + "If you specify a solution file then packaging must be " + MSBuildPackaging.MSBUILD_SOLUTION;
                  getLog().error( msg );
                  throw new MojoExecutionException( msg );
              }
              return;
          }
          String prefix = "Missing projectFile";
          if ( projectFile != null )
          {
              prefix = ". The specified projectFile '" + projectFile
                      + "' is not valid";
          }
          throw new MojoExecutionException( prefix
                  + ", please check your configuration" );
      }