fix(python): warn on dynamic pyproject.toml versioning (#1983)

This PR makes sure that people that use dynamic versioning in the `pyproject.toml`
file receive a warning instead of an error. See #1804.

Co-authored-by: Jeff Ching <chingor@google.com>

src/updaters/python/pyproject-toml.ts

@@ -13,15 +13,16 @@
 // limitations under the License.
 
 import * as TOML from '@iarna/toml';
-import {replaceTomlValue} from '../../util/toml-edit';
 import {logger as defaultLogger, Logger} from '../../util/logger';
+import {replaceTomlValue} from '../../util/toml-edit';
 import {DefaultUpdater} from '../default';
 
 // TODO: remove support for `poetry.tool` when Poetry will use `project`.
 
 interface PyProjectContent {
   name: string;
   version: string;
+  dynamic?: string[];
 }
 
 /**
@@ -52,6 +53,14 @@ export class PyProjectToml extends DefaultUpdater {
     const project = parsed.project || parsed.tool?.poetry;
 
     if (!project?.version) {
+      // Throw warning if the version is dynamically generated.
+      if (project?.dynamic && project.dynamic.includes('version')) {
+        const msg =
+          "dynamic version found in 'pyproject.toml'. Skipping update.";
+        logger.warn(msg);
+        return content;
+      }
+
       const msg = 'invalid file';
       logger.error(msg);
       throw new Error(msg);