Added a user-friendly output to an import error

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipatests/test_integration/env_config.py

@@ -107,7 +107,11 @@ def get_global_config(env=None):
 
 def config_from_env(env):
     if 'IPATEST_YAML_CONFIG' in env:
-        import yaml
+        try:
+            import yaml
+        except ImportError as e:
+            raise ImportError("%s, please install PyYAML package to fix it" %
+                              e.message)
         with open(env['IPATEST_YAML_CONFIG']) as file:
             confdict = yaml.safe_load(file)
             return Config.from_dict(confdict)