Description of problem:
virt-manager does not check to see if there is adequate disk space in the target
directory/mount point when installing to simple file.


Version-Release number of selected component (if applicable):
virt-manager-0.4.0-3.el5


How reproducible:
always

Steps to Reproduce:
1. note amount of disk space in /opt
2. create a new vm disk in /opt that exceeds the free space.
3. virt-manager is happily start allocating blocks and then fails the complete
disk creation due to lack of space
  
Actual results:


Expected results:

1. should check for free space in target directory
2. - provide error condition and option to reselect location and/or size