Could not retrieve lockfile (pcsg/composer-assets requirement)

I'm trying to install QUIQQER in version 1.1.
After starting the setup I get the following error

[INFO] - Starte Composer. Dies könnte eine Weile dauern.

( ! ) Fatal error: 
Uncaught Exception: 
Could not retireve the lockfile: 
Could not retrieve lockfile: 
Composer Error: Loading composer repositories with package information Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages. 
Problem 1 - Conclusion: remove pcsg/composer-assets 1.0.1 - Conclusion: don't install pcsg/composer-assets 1.0.1 - quiqqer/quiqqer 1.1.0 requires pcsg/composer-assets dev-master|dev-dev -> satisfiable by pcsg/composer-assets[dev-dev, dev-master]. - quiqqer/quiqqer 1.1.1 requires pcsg/composer-assets dev-master|dev-dev -> satisfiable by pcsg/composer-assets[dev-dev, dev-master]. - Can only install one of: pcsg/composer-assets[1.0.1, dev-dev]. - Can only install one of: pcsg/composer-assets[1.0.1, dev-master]. - Installation request for pcsg/composer-assets (locked at 1.0.1, required as ^1.0.1|dev-dev|dev-master) -> satisfiable by pcsg/composer-assets[1.0.1]. - Installation request for quiqqer/quiqqer ~1.1.0 in /var/www/quiqqer-test/src/QUI/Setup/Setup.php on line 1342  
  
( ! ) Exception: 
Could not retireve the lockfile: 
Could not retrieve lockfile: 
Composer Error: 
Loading composer repositories with package information 
Updating dependencies (including require-dev) 
Your requirements could not be resolved to an installable set of packages. 
Problem 1 - Conclusion: remove pcsg/composer-assets 1.0.1 - Conclusion: don't install pcsg/composer-assets 1.0.1 - quiqqer/quiqqer 1.1.0 requires pcsg/composer-assets dev-master|dev-dev -> satisfiable by pcsg/composer-assets[dev-dev, dev-master]. - quiqqer/quiqqer 1.1.1 requires pcsg/composer-assets dev-master|dev-dev -> satisfiable by pcsg/composer-assets[dev-dev, dev-master]. - Can only install one of: pcsg/composer-assets[1.0.1, dev-dev]. - Can only install one of: pcsg/composer-assets[1.0.1, dev-master]. - Installation request for pcsg/composer-assets (locked at 1.0.1, required as ^1.0.1|dev-dev|dev-master) -> satisfiable by pcsg/composer-assets[1.0.1]. - Installation request for quiqqer/quiqqer ~1.1.0 -> satisfiable by quiqqer/quiqqer[1.1.0, 1.1.1]. in /var/www/quiqqer-test/src/QUI/Setup/Setup.php on line 1342  
  
Call Stack  
#	Time	Memory	Function	Location
1	0.0000	357616	{main}( )	.../iframe.php:0
2	0.0007	462136	installQUIQQER( )	.../iframe.php:85
3	0.0009	466352	QUI\Setup\Setup->runSetup( )	.../iframe.php:148
4	0.0010	467632	QUI\Setup\Setup->setupComposerInstallQuiqqer( )	.../Setup.php:240