raise report level for some shed linting

I think these are all cases which lead to errors in deploying.

fixes https://github.com/galaxyproject/tools-iuc/issues/3384

planemo/shed_lint.py

@@ -291,13 +291,13 @@ def lint_shed_yaml(realized_repository, lint_ctx):
     path = realized_repository.real_path
     shed_yaml = os.path.join(path, ".shed.yml")
     if not os.path.exists(shed_yaml):
-        lint_ctx.info("No .shed.yml file found, skipping.")
+        lint_ctx.error("No .shed.yml file found, skipping.")
         return
     try:
         with open(shed_yaml, "r") as fh:
             yaml.safe_load(fh)
     except Exception as e:
-        lint_ctx.warn("Failed to parse .shed.yml file [%s]" % unicodify(e))
+        lint_ctx.error("Failed to parse .shed.yml file [%s]" % unicodify(e))
         return
     lint_ctx.info(".shed.yml found and appears to be valid YAML.")
     _lint_shed_contents(lint_ctx, realized_repository)
@@ -311,7 +311,7 @@ def _lint_if_present(key, func, *args):
         if value is not None:
             msg = func(value, *args)
             if msg:
-                lint_ctx.warn(msg)
+                lint_ctx.error(msg)
 
     _lint_if_present("owner", validate_repo_owner)
     _lint_if_present("name", validate_repo_name)