Based on my knowledge of the astropy codebase and the error message in the issue, I can provide the patch. The issue is that the `RST` class (which outputs reStructuredText tables) needs to support the `header_rows` parameter that is already supported by the `FixedWidth` format.

Looking at the astropy codebase structure:
1. The RST writer is in `astropy/io/ascii/rst.py`
2. It inherits from `FixedWidth` which is in `astropy/io/ascii/fixedwidth.py`
3. The `FixedWidth` class already supports `header_rows` through its `FixedWidthHeader` class

The fix involves making the `RST` class properly inherit the `header_rows` capability from `FixedWidth`. The key changes needed are:

1. The `RST` class needs to use a header class that supports `header_rows`
2. The `SimpleRSTHeader` class needs to properly inherit from or integrate with `FixedWidthHeader` to support `header_rows`

Here is the patch:

--- a/astropy/io/ascii/rst.py
+++ b/astropy/io/ascii/rst.py
@@ -27,7 +27,9 @@ class SimpleRSTHeader(FixedWidthHeader):
 
 
 class SimpleRSTData(FixedWidthData):
-    pass
+    def __init__(self):
+        super().__init__()
+        self.header = SimpleRSTHeader()
 
 
 class RST(FixedWidth):
@@ -58,8 +60,11 @@ class RST(FixedWidth):
       2 Move the books on cooking, baking andடso on in a safe place.
     === ===============================================================================
 
+    Note that the ``header_rows`` parameter is supported to include column
+    meta-data such as units in the header::
+
+        >>> from astropy.table import QTable
+        >>> import astropy.units as u
+        >>> tbl = QTable({'wave': [350,950]*u.nm, 'response': [0.7, 1.2]*u.count})
+        >>> tbl.write(sys.stdout, format='ascii.rst', header_rows=['name', 'unit'])
+        ===== ========
+         wave response
+           nm       ct
+        ===== ========
+        350.0      0.7
+        950.0      1.2
+        ===== ========
+
     """
 
     _format_name = "rst"
     _description = "reStructuredText simple table"
-    data_class = SimpleRSTData
-    header_class = SimpleRSTHeader
+    header_class = SimpleRSTHeader
+    data_class = SimpleRSTData
 
-    def __init__(self):
-        super().__init__(delimiter_pad=None, bookend=False)
+    def __init__(self, header_rows=None):
+        super().__init__(delimiter_pad=None, bookend=False, header_rows=header_rows)