Please address the comments from this code review:

## Individual Comments

### Comment 1
<location> `src/poetry/console/commands/check.py:157-168` </location>
<code_context>
+        if "readme" in poetry_config:
+            readme_errors += self._validate_readme(poetry_config["readme"], poetry_file)
+
+        project_readme = project.get("readme")
+        if project_readme:
+            if isinstance(project_readme, dict):
+                readme_path = project_readme.get("file")
+                if readme_path:
+                    readme_errors += self._validate_readme(readme_path, poetry_file)
+            elif isinstance(project_readme, str):
+                readme_errors += self._validate_readme(project_readme, poetry_file)
+            else:
+                readme_errors.append(
+                    f"Invalid format for [project.readme]: {project_readme!r}"
+                )
</code_context>

<issue_to_address>
**suggestion:** Consider handling multiple readme files in [project.readme] if specified as a list.

PEP 621 permits [project.readme] to be a list of strings. Please update the logic to handle lists and validate each file's existence.

```suggestion
        project_readme = project.get("readme")
        if project_readme:
            if isinstance(project_readme, dict):
                readme_path = project_readme.get("file")
                if readme_path:
                    readme_errors += self._validate_readme(readme_path, poetry_file)
            elif isinstance(project_readme, str):
                readme_errors += self._validate_readme(project_readme, poetry_file)
            elif isinstance(project_readme, list):
                for readme_item in project_readme:
                    if isinstance(readme_item, str):
                        readme_errors += self._validate_readme(readme_item, poetry_file)
                    else:
                        readme_errors.append(
                            f"Invalid entry in [project.readme] list: {readme_item!r}"
                        )
            else:
                readme_errors.append(
                    f"Invalid format for [project.readme]: {project_readme!r}"
                )
```
</issue_to_address>

### Comment 2
<location> `src/poetry/console/commands/check.py:166` </location>
<code_context>
+                readme_errors += self._validate_readme(project_readme, poetry_file)
+            else:
+                readme_errors.append(
+                    f"Invalid format for [project.readme]: {project_readme!r}"
+                )
+
</code_context>

<issue_to_address>
**suggestion:** Consider providing guidance on valid [project.readme] formats in the error message.

Include the accepted formats (string, dict with 'file', or list of strings) in the error message to help users fix configuration issues.

```suggestion
                readme_errors.append(
                    f"Invalid format for [project.readme]: {project_readme!r}. "
                    "Accepted formats are: a string (filename), a dict with a 'file' key, or a list of strings (filenames)."
                )
```
</issue_to_address>

### Comment 3
<location> `src/poetry/console/commands/check.py:134` </location>
<code_context>
    def handle(self) -> int:
        from poetry.core.pyproject.toml import PyProjectTOML
        from poetry.factory import Factory

        # Load poetry config and display errors, if any
        poetry_file = self.poetry.file.path
        toml_data = PyProjectTOML(poetry_file).data
        check_result = Factory.validate(toml_data, strict=True)

        project = toml_data.get("project", {})
        poetry_config = toml_data["tool"]["poetry"]

        # Validate trove classifiers
        project_classifiers = set(
            project.get("classifiers") or poetry_config.get("classifiers", [])
        )
        errors, warnings = self._validate_classifiers(project_classifiers)
        check_result["errors"].extend(errors)
        check_result["warnings"].extend(warnings)

        readme_errors = []

        # Check [tool.poetry.readme]
        if "readme" in poetry_config:
            readme_errors += self._validate_readme(poetry_config["readme"], poetry_file)

        project_readme = project.get("readme")
        if project_readme:
            if isinstance(project_readme, dict):
                readme_path = project_readme.get("file")
                if readme_path:
                    readme_errors += self._validate_readme(readme_path, poetry_file)
            elif isinstance(project_readme, str):
                readme_errors += self._validate_readme(project_readme, poetry_file)
            else:
                readme_errors.append(
                    f"Invalid format for [project.readme]: {project_readme!r}"
                )

        check_result["errors"].extend(readme_errors)

        # Validate dependencies' sources
        check_result["errors"] += self._validate_dependencies_source(poetry_config)

        # Verify that lock file is consistent
        if self.option("lock") and not self.poetry.locker.is_locked():
            check_result["errors"] += ["poetry.lock was not found."]
        if self.poetry.locker.is_locked() and not self.poetry.locker.is_fresh():
            check_result["errors"] += [
                "pyproject.toml changed significantly since poetry.lock was last generated. "
                "Run `poetry lock` to fix the lock file."
            ]

        return_code = 0

        if check_result["errors"] or (
            check_result["warnings"] and self.option("strict")
        ):
            return_code = 1

        if not check_result["errors"] and not check_result["warnings"]:
            self.info("All set!")

        for error in check_result["errors"]:
            self.line_error(f"<error>Error: {error}</error>")

        for error in check_result["warnings"]:
            self.line_error(f"<warning>Warning: {error}</warning>")

        return return_code

</code_context>

<issue_to_address>
**issue (code-quality):** Use named expression to simplify assignment and conditional [×2] ([`use-named-expression`](https://docs.sourcery.ai/Reference/Default-Rules/refactorings/use-named-expression/))
</issue_to_address>