diff --git a/pandas/io/excel/_base.py b/pandas/io/excel/_base.py
index ed5943e9a1698..8f7bf8e0466f9 100644
--- a/pandas/io/excel/_base.py
+++ b/pandas/io/excel/_base.py
@@ -590,9 +590,8 @@ def __new__(cls, path, engine=None, **kwargs):
                     if engine == 'auto':
                         engine = _get_default_writer(ext)
                 except KeyError:
-                    error = ValueError("No engine for filetype: '{ext}'"
-                                       .format(ext=ext))
-                    raise error
+                    raise ValueError("No engine for filetype: '{ext}'"
+                                     .format(ext=ext))
             cls = get_writer(engine)
 
         return object.__new__(cls)
diff --git a/pandas/io/excel/_util.py b/pandas/io/excel/_util.py
index 1aeaf70f0832e..630503765b34a 100644
--- a/pandas/io/excel/_util.py
+++ b/pandas/io/excel/_util.py
@@ -7,6 +7,7 @@
 
 from pandas.core import config
 
+# Default extentions to use default Excel writers classes.
 _writer_extensions = ["xlsx", "xls", "xlsm"]
 
 
@@ -31,6 +32,8 @@ def register_writer(klass):
 
 
 def _get_default_writer(ext):
+    """Get default an instantiated writer class using extention.
+    """
     _default_writers = {'xlsx': 'openpyxl', 'xlsm': 'openpyxl', 'xls': 'xlwt'}
     try:
         import xlsxwriter  # noqa
@@ -230,8 +233,6 @@ def _fill_mi_header(row, control_row):
 
     return _maybe_convert_to_string(row), control_row
 
-# fill blank if index_col not None
-
 
 def _pop_header_name(row, index_col):
     """