Add test for fixed-width failure

CHANGES.rst

@@ -5,7 +5,6 @@
   (`Issue #140 <https://github.com/sqlalchemy-redshift/sqlalchemy-redshift/pull/140>`_)
 - Add support for Parquet and ORC file formats in the COPY command
   (`Issue #151 <https://github.com/sqlalchemy-redshift/sqlalchemy-redshift/pull/150>`_)
-- Add official support for Python 3.7
 
 
 0.7.1 (2018-01-17)

tests/test_copy_command.py

@@ -1,5 +1,6 @@
 import pytest
 import sqlalchemy as sa
+from sqlalchemy import exc as sa_exc
 
 from sqlalchemy_redshift import dialect
 from sqlalchemy_redshift import commands
@@ -134,6 +135,19 @@ def test_invalid_format():
         )
 
 
+def test_fixed_width_format_without_widths():
+    copy = dialect.CopyCommand(
+        tbl,
+        format=commands.Format.fixed_width,
+        data_location='s3://bucket',
+        access_key_id=access_key_id,
+        secret_access_key=secret_access_key
+    )
+    with pytest.raises(sa_exc.CompileError,
+                       match=r"^'fixed_width' argument required.*$"):
+        compile_query(copy)
+
+
 def test_compression():
     expected_result = """
     COPY schema1.t1 FROM 's3://mybucket/data/listing/'