Description of problem:
Running "zanata glossary push" in a empty (non-zanata) dir say
gives a backtrace, not an error message.

Version-Release number of selected component (if applicable):
zanata-python-client-1.3.4-1.fc16

How reproducible:
every time

Steps to Reproduce:
$ mkdir test
$ cd test
$ zanata glossary push
  
Actual results:
Traceback (most recent call last):
  File "/usr/bin/zanata", line 25, in <module>
    zanata.run()
  File "/usr/lib/python2.7/site-packages/zanataclient/zanata.py", line 1369, in run
    program_name=os.path.split(sys.argv[0])[1],
  File "/usr/lib/python2.7/site-packages/zanataclient/command.py", line 339, in handle_program
    command(command_options, args)
  File "/usr/lib/python2.7/site-packages/zanataclient/zanata.py", line 1291, in glossary_push
    url, username, apikey = optionsutil.apply_configfiles()
  File "/usr/lib/python2.7/site-packages/zanataclient/optionsutil.py", line 41, in apply_configfiles
    url = self.apply_project_config()
  File "/usr/lib/python2.7/site-packages/zanataclient/optionsutil.py", line 66, in apply_project_config
    self.project_config = self.config.read_project_config(path)
  File "/usr/lib/python2.7/site-packages/zanataclient/parseconfig.py", line 74, in read_project_config
    if os.path.getsize(filename) == 0:
  File "/usr/lib64/python2.7/genericpath.py", line 49, in getsize
    return os.stat(filename).st_size
OSError: [Errno 2] No such file or directory: '/home/petersen/test/zanata.xml'

Expected results:
Just something like "Missing 'zanata.xml' file?

Additional info:
I think better to avoid backtraces and catch
errors like the above one with a friendly error message.