Error: exception-handler returned

	Call history:

	dbc-supplier-test.scm:10: g373	  
	dbc-supplier-test.scm:10: open-output-string	  
	dbc-supplier-test.scm:10: ##sys#check-output-port	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#print	  
	dbc-supplier-test.scm:10: ##sys#write-char-0	  
	dbc-supplier-test.scm:10: get-output-string	  
	dbc-supplier-test.scm:10: error	  
	dbc-supplier-test.scm:10: k307	  
	dbc-supplier-test.scm:10: g311	  
	dbc-supplier-test.scm:10: dbc#make-contract-condition	  
	dbc-supplier-test.scm:10: signal	  	<--