Description of problem:

spacewalk-clone-by-date does not handle correctly invalid configuration  file.

Version-Release number of selected component (if applicable):

spacewalk-utils-1.7.15-38


How reproducible:
100%

Steps to Reproduce:
1. Create custom software chhannel: test_x86_64
2. Add/push some packages in it.
3. Make sure the repodata is generated for the channel

    #ll /var/cache/rhn/repodata/test_x86_64

4. Create incorrect configuration file (there is a extra space after channel name)
cat > clone_1.conf <<EOF
{
 "username":"admin",
 "password":"nimda",
 "assumeyes":true,
 "skip_depsolve":false,
"blacklist": {
              },
 "removelist": {
              },
 "channels":[
             {
                "test_x86_64 ": "clone-test_x86_64"
             }
           ]
}
EOF

5.# spacewalk-clone-by-date --config clone_1.conf
Reading repository information.

By continuing the following channels will be created: 
clone-test_x86_64
Cloning test_x86_64  to clone-test_x86_64 with original package set.

DEBUG ADDED BY DY:repos = [{"id":label, "relative_path":repodata(label)} for label in labels]
[{'id': 'test_x86_64 ', 'relative_path': '/var/cache/rhn/repodata/test_x86_64 '}]

Copying repodata, please wait.

Unable to read repository information.
                Please verify repodata has been generated in /var/cache/rhn/repodata/LABEL.
                Error from yum: Cannot retrieve repository metadata (repomd.xml) for repository: test_x86_64 . Please verify its path and try again


Actual results:
The problem in the configuration file is discovered too late.
As a side effect a new folder is created by function create_repodata_link() (cloneByDate.py):

#ll /var/cache/rhn/repodata/test_x86_64\ /

This folder will not be removed by 

def remove_repodata_link(link_path):
    if os.path.exists(link_path):
        return os.unlink(link_path)


even if Bug 870794 will be solved.
 
Expected results:
The problem is discovered at the very beginning.
Probably in file spacewalk-clone-by-date

 try:
        config = json.load(open(options.config))
    except:
        raise UserError("Configuration file is invalid, please check syntax.")


Additional info:

def dep_solve(self, nvrea_list, labels=None):             
        if not labels:
            labels = self.channel_map.keys()
        repos = [{"id":label, "relative_path":repodata(label)} for label in labels]

        print "Copying repodata, please wait."

        # dep solver expects the metadata to be in /repodata directory;
        # create temporary symlinks
        temp_repo_links = []
        for repo in repos:
            yum_repodata_path = "%s/repodata" % (repo['relative_path'])
            create_repodata_link(repo['relative_path'], yum_repodata_path)
            temp_repo_links.append(yum_repodata_path)
        try:
            solver = DepSolver(repos, nvrea_list)
            dep_results = solver.processResults(solver.getDependencylist())
            solver.cleanup()
            self.process_deps(dep_results)
        except RepoError, e:
            raise UserError("""Unable to read repository information.
                Please verify repodata has been generated in /var/cache/rhn/repodata/LABEL.
                Error from yum: %s""" % e.value)
        
        # clean up temporary symlinks
        for link in temp_repo_links:
            remove_repodata_link(link)
            
            
            
def create_repodata_link(src_path, dst_path):
    if not os.path.exists(os.path.dirname(dst_path)):
        # create a dir if missing
        os.makedirs(os.path.dirname(dst_path))
    if not os.path.exists(dst_path):
        if os.path.lexists(dst_path):
            # remove dead links
            os.unlink(dst_path)
        # create the link
        os.symlink(src_path, dst_path)
        
        
def remove_repodata_link(link_path):
    if os.path.exists(link_path):
        return os.unlink(link_path)