Fix AttributeError: "load()" has been removed

ruamel.yaml 0.18 has removed `load()` which lets the test fail:

```
AttributeError:
"load()" has been removed, use

  yaml = YAML(typ='rt')
  yaml.load(...)

and register any classes that you use, or check the tag attribute on the loaded data,
instead of file "ionit.py", line 126

                    file_context = yaml.load(config_file, Loader=yaml.SafeLoader)
```

Use the new ruamel.yaml API in case ruamel.yaml is used.

Author: bdrung

ionit

@@ -85,6 +85,16 @@ def load_python_plugin(file_path, current_context):
     return context
 
 
+def load_yaml(stream):
+    """Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+    """
+    if hasattr(yaml, "YAML"):
+        yaml_object = yaml.YAML(typ="safe")
+        return yaml_object.load(stream)
+    return yaml.load(stream, Loader=yaml.SafeLoader)
+
+
 def get_config_files(paths):
     """Return files for the given paths (could either be files or directories)."""
     logger = logging.getLogger(SCRIPT_NAME)
@@ -123,7 +133,7 @@ def collect_context(paths, encoding):
             elif extension == ".yaml":
                 logger.info("Reading configuration file '%s'...", file)
                 with open(file, encoding=encoding) as config_file:
-                    file_context = yaml.load(config_file, Loader=yaml.SafeLoader)
+                    file_context = load_yaml(config_file)
             else:
                 logger.info(
                     "Skipping configuration file '%s', "

tests/test_ionit.py

@@ -150,7 +150,8 @@ def test_invalid_yaml(self):
                 (
                     "ERROR:ionit:Failed to read YAML from "
                     r"'[^']*config/invalid-yaml/invalid.yaml': mapping values are not allowed "
-                    r"here\s+in \"\S*config/invalid-yaml/invalid.yaml\", line 3, column 14"
+                    r"(here|in this context)\s+"
+                    r"in \"\S*config/invalid-yaml/invalid.yaml\", line 3, column 14"
                 ),
             )