strip new lines from get_build_error_message output, so the output is

same as before only on 1 line

* CLOUDBLD-8281

Signed-off-by: Robert Cerven <rcerven@redhat.com>

koji_containerbuild/plugins/builder_containerbuild.py

@@ -547,7 +547,7 @@ def sigint_handler(*args, **kwargs):
 
             if error_message:
                 raise ContainerError('Image build failed. %s. OSBS build id: %s' %
-                                     (error_message, build_id))
+                                     (' '.join(error_message.split('\n')), build_id))
             else:
                 raise ContainerError('Image build failed. OSBS build id: %s' %
                                      build_id)