fix(pypi): skip compatibility check if not a version

Closes #6142

lib/datasource/pypi/index.ts

@@ -4,6 +4,7 @@ import { parse } from 'node-html-parser';
 import { logger } from '../../logger';
 import { Http } from '../../util/http';
 import { matches } from '../../versioning/pep440';
+import * as pep440 from '../../versioning/pep440';
 import { GetReleasesConfig, ReleaseResult } from '../common';
 
 export const id = 'pypi';
@@ -19,7 +20,7 @@ function compatibleVersions(
   compatibility: Record<string, string>
 ): string[] {
   const versions = Object.keys(releases);
-  if (!(compatibility && compatibility.python)) {
+  if (!(compatibility?.python && pep440.isVersion(compatibility.python))) {
     return versions;
   }
   return versions.filter((version) =>

lib/versioning/pep440/index.ts

@@ -47,7 +47,7 @@ export const isSingleVersion = (constraint: string): string =>
   isVersion(constraint) ||
   (constraint.startsWith('==') && isVersion(constraint.substring(2).trim()));
 
-export { matches };
+export { isVersion, matches };
 
 export const api: VersioningApi = {
   equals,