Improve YML parsing error output

contentctl/input/yml_reader.py

@@ -1,7 +1,8 @@
-from typing import Dict, Any
-import yaml
-import sys
 import pathlib
+import sys
+from typing import Any, Dict
+
+import yaml
 
 
 class YmlReader:
@@ -13,40 +14,44 @@ def load_file(
     ) -> Dict[str, Any]:
         try:
             file_handler = open(file_path, "r", encoding="utf-8")
+        except OSError as exc:
+            print(
+                f"\nThere was an unrecoverable error when opening the file '{file_path}' - we will exit immediately:\n{str(exc)}"
+            )
+            sys.exit(1)
 
             # The following code can help diagnose issues with duplicate keys or
             # poorly-formatted but still "compliant" YML.  This code should be
             # enabled manually for debugging purposes. As such, strictyaml
             # library is intentionally excluded from the contentctl requirements
 
+        try:
             if STRICT_YML_CHECKING:
+                # This is an extra level of verbose parsing that can be
+                # enabled for debugging purpose. It is intentionally done in
+                # addition to the regular yml parsing
                 import strictyaml
 
-                try:
-                    strictyaml.dirty_load(file_handler.read(), allow_flow_style=True)
-                    file_handler.seek(0)
-                except Exception as e:
-                    print(f"Error loading YML file {file_path}: {str(e)}")
-                    sys.exit(1)
-            try:
-                # Ideally we should use
-                # from contentctl.actions.new_content import NewContent
-                # and use NewContent.UPDATE_PREFIX,
-                # but there is a circular dependency right now which makes that difficult.
-                # We have instead hardcoded UPDATE_PREFIX
-                UPDATE_PREFIX = "__UPDATE__"
-                data = file_handler.read()
-                if UPDATE_PREFIX in data:
-                    raise Exception(
-                        f"The file {file_path} contains the value '{UPDATE_PREFIX}'. Please fill out any unpopulated fields as required."
-                    )
-                yml_obj = yaml.load(data, Loader=yaml.CSafeLoader)
-            except yaml.YAMLError as exc:
-                print(exc)
-                sys.exit(1)
-
-        except OSError as exc:
-            print(exc)
+                strictyaml.dirty_load(file_handler.read(), allow_flow_style=True)
+                file_handler.seek(0)
+
+            # Ideally we should use
+            # from contentctl.actions.new_content import NewContent
+            # and use NewContent.UPDATE_PREFIX,
+            # but there is a circular dependency right now which makes that difficult.
+            # We have instead hardcoded UPDATE_PREFIX
+            UPDATE_PREFIX = "__UPDATE__"
+            data = file_handler.read()
+            if UPDATE_PREFIX in data:
+                raise Exception(
+                    f"\nThe file {file_path} contains the value '{UPDATE_PREFIX}'. Please fill out any unpopulated fields as required."
+                )
+            yml_obj = yaml.load(data, Loader=yaml.CSafeLoader)
+
+        except yaml.YAMLError as exc:
+            print(
+                f"\nThere was an unrecoverable YML Parsing error when reading or parsing the file '{file_path}' - we will exit immediately:\n{str(exc)}"
+            )
             sys.exit(1)
 
         if add_fields is False: