[FIX] yaml: Specify loader to YAML constructors

pyYAML 5.1 is now the distro version. This introduces the FullLoader as
the default loader used with yaml.load(…), however, the default loader for
yaml.add_constructor(…) has not been updated (this is a known issue:
yaml/pyyaml#274).
This commit specifies the loader to be used when adding constructors,
using the FullLoader if it exists and the older Loader if not (i.e.
depending on which version of pyYAML is installed).

Task: 3958

Signed-off-by: Samuel Searles-Bryant <samuel.searles-bryant@unipart.io>

odoo/tools/yaml_tag.py

@@ -149,16 +149,24 @@ def ref_constructor(loader, tag_suffix, node):
 # Constructors are actually defined globally: do not redefined them in another
 # class/file/package.  This means that module recorder need import this file.
 def add_constructors():
-    yaml.add_constructor(u"!assert", assert_constructor)
-    yaml.add_constructor(u"!record", record_constructor)
-    yaml.add_constructor(u"!python", python_constructor)
-    yaml.add_constructor(u"!menuitem", menuitem_constructor)
-    yaml.add_constructor(u"!act_window", act_window_constructor)
-    yaml.add_constructor(u"!function", function_constructor)
-    yaml.add_constructor(u"!report", report_constructor)
-    yaml.add_constructor(u"!context", context_constructor)
-    yaml.add_constructor(u"!delete", delete_constructor)
-    yaml.add_constructor(u"!url", url_constructor)
-    yaml.add_constructor(u"!eval", eval_constructor)
-    yaml.add_multi_constructor(u"!ref", ref_constructor)
+    constructors = [
+        ("!assert", assert_constructor),
+        ("!record", record_constructor),
+        ("!python", python_constructor),
+        ("!menuitem", menuitem_constructor),
+        ("!act_window", act_window_constructor),
+        ("!function", function_constructor),
+        ("!report", report_constructor),
+        ("!context", context_constructor),
+        ("!delete", delete_constructor),
+        ("!url", url_constructor),
+        ("!eval", eval_constructor),
+        ("!ref", ref_constructor),
+    ]
+    try:
+        loader = yaml.FullLoader  # default for pyYAML>=5.1. Does not exist in earlier versions.
+    except AttributeError:
+        loader = yaml.Loader  # default for pyYAML<5.1
+    for tag, constructor in constructors:
+        yaml.add_constructor(tag, constructor, Loader=loader)
 add_constructors()