Fix invalid Python import for qualified package name (#14015)

* Add unittest for toModelImport

* Use `packageName` insetad of `packagePath()`

Author: loleary

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java

@@ -889,7 +889,7 @@ public String toDefaultValue(Schema p) {
     @Override
     public String toModelImport(String name) {
         // name looks like Cat
-        return "from " + packagePath() + "." +  modelPackage() + "." + toModelFilename(name) + " import " + toModelName(name);
+        return "from " + packageName + "." +  modelPackage() + "." + toModelFilename(name) + " import " + toModelName(name);
     }
 
     @Override

modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientTest.java

@@ -224,4 +224,13 @@ public void testEnumNames() {
         Assert.assertEquals(enumVars.get(0).get("name"), "DIGIT_THREE_67B9C");
         Assert.assertEquals(enumVars.get(1).get("name"), "FFA5A4");
     }
+
+    @Test(description = "format imports of models using a package containing dots")
+    public void testImportWithQualifiedPackageName() throws Exception {
+        final PythonClientCodegen codegen = new PythonClientCodegen();
+        codegen.setPackageName("openapi.client");
+
+        String importValue = codegen.toModelImport("model_name");
+        Assert.assertEquals(importValue, "from openapi.client.model.model_name import ModelName");
+    }
 }