code: public function download(PackageInterface $package, $path)
      {
          if (!$package->getSourceReference()) {
              throw new \InvalidArgumentException('Package '.$package->getPrettyName().' is missing reference information');
          }
  
          $this->io->writeError("  - Installing <info>" . $package->getName() . "</info> (<comment>" . $package->getFullPrettyVersion() . "</comment>): ", false);
          $this->filesystem->emptyDirectory($path);
  
          $urls = $package->getSourceUrls();
          while ($url = array_shift($urls)) {
              try {
                  if (Filesystem::isLocalPath($url)) {
                      // realpath() below will not understand
                      // url that starts with "file://"
                      $needle = 'file://';
                      $isFileProtocol = false;
                      if (0 === strpos($url, $needle)) {
                          $url = substr($url, strlen($needle));
                          $isFileProtocol = true;
                      }
  
                      // realpath() below will not understand %20 spaces etc.
                      if (false !== strpos($url, '%')) {
                          $url = rawurldecode($url);
                      }
  
                      $url = realpath($url);
  
                      if ($isFileProtocol) {
                          $url = $needle . $url;
                      }
                  }
                  $this->doDownload($package, $path, $url);
                  break;
              } catch (\Exception $e) {
                  // rethrow phpunit exceptions to avoid hard to debug bug failures
                  if ($e instanceof \PHPUnit_Framework_Exception) {
                      throw $e;
                  }
                  if ($this->io->isDebug()) {
                      $this->io->writeError('Failed: ['.get_class($e).'] '.$e->getMessage());
                  } elseif (count($urls)) {
                      $this->io->writeError('    Failed, trying the next URL');
                  }
                  if (!count($urls)) {
                      throw $e;
                  }
              }
          }
      }
docs: {@inheritDoc}