Use FlatpakGenerator.build_module_as_[yaml_]str in main.

These methods implement formatting, so why duplicate that code. Fixes #45.

* req2flatpak.py (main)

req2flatpak.py

@@ -808,14 +808,16 @@ def main():  # pylint: disable=too-many-branches
     }
 
     # generate flatpak-builder build module
-    build_module = FlatpakGenerator.build_module(requirements, downloads)
-
     if options.yaml:
-        yaml.dump(build_module, output_stream, default_flow_style=False)
-        parser.exit()
-
-    # write output
-    json.dump(build_module, output_stream, indent=4)
+        # write yaml
+        output_stream.write(
+            FlatpakGenerator.build_module_as_yaml_str(requirements, downloads)
+        )
+    else:
+        # write json
+        output_stream.write(
+            FlatpakGenerator.build_module_as_str(requirements, downloads)
+        )
 
 
 if __name__ == "__main__":

tests/test_req2flatpak.py

@@ -91,7 +91,7 @@ def validate_build_module(self, build_module: dict) -> None:
     @contextmanager
     def requirements_file(
         self,
-    ) -> Generator[tempfile._TemporaryFileWrapper[str], None, None]:
+    ) -> Generator[tempfile._TemporaryFileWrapper, None, None]:
         """Create a temporary requirements file."""
         with tempfile.NamedTemporaryFile(mode="w+", encoding="utf-8") as req_file:
             req_file.write("\n".join(self.requirements))