Strip trailing whitespaces @ EOL when dumping FST

It's a workaround for PyCQA/redbaron#190

migrate.py

@@ -231,6 +231,11 @@ def write_text_into_file(path, text):
         return f.write(text)
 
 
+def write_fst_into_file(path, fst):
+    """Dump fst into the given file path."""
+    write_text_into_file(path, fst.dumps().rstrip())
+
+
 @contextlib.contextmanager
 def working_directory(target_dir):
     """Temporary change dir to the target and change back on exit."""
@@ -733,12 +738,12 @@ def rewrite_py(src, dest, collection, spec, namespace, args):
 
     rewrite_class_property(mod_fst, collection, namespace, dest)
 
-    plugin_data_new = mod_fst.dumps()
+    plugin_data_new = mod_fst.dumps().rstrip()
 
     if mod_src_text != plugin_data_new:
         logger.info('Rewriting plugin references in %s', dest)
 
-    write_text_into_file(dest, plugin_data_new)
+    write_fst_into_file(dest, mod_fst)
 
     return (import_deps, docs_deps)
 
@@ -1367,7 +1372,7 @@ def rewrite_unit_tests(collection_dir, collection, spec, namespace, args):
         _unit_test_module_src_text, unit_test_module_fst = read_module_txt_n_fst(file_path)
         deps += rewrite_imports(unit_test_module_fst, collection, spec, namespace, args)
         deps += rewrite_unit_tests_patch(unit_test_module_fst, collection, spec, namespace, args)
-        write_text_into_file(file_path, unit_test_module_fst.dumps())
+        write_fst_into_file(file_path, unit_test_module_fst)
 
     return deps