check for existance of configuration file.

lib/cfg.py

@@ -5,8 +5,16 @@ import os, sys
 import ConfigParser
 from utils import *
 
-cfg = ConfigParser.ConfigParser()
 config_file_path = os.path.join(os.path.dirname(sys.argv[0]),'config')
+if not os.path.exists(config_file_path):
+    print '''
+The configuration file '%s' does not exist.
+Please create this file and fill in the configuration data
+of your certificates so that 'cam' can operate.
+'''
+    sys.exit(1)
+
+cfg = ConfigParser.ConfigParser()
 cfg.read(config_file_path)
 ca = cfg2dict(cfg, 'ca')
 ca_base = cfg.get('global', 'root')