revert supported pyodbc version

Author: michiya

README.rst

@@ -31,7 +31,7 @@ Dependencies
 ------------
 
 -  Django 2.0.1
--  pyodbc 4.0 or newer
+-  pyodbc 3.0 or newer
 
 Installation
 ------------

setup.py

@@ -29,7 +29,7 @@
     packages=['sql_server', 'sql_server.pyodbc'],
     install_requires=[
         'Django>=2.0.1,<2.1',
-        'pyodbc>=4.0',
+        'pyodbc>=3.0',
     ],
     classifiers=CLASSIFIERS,
     keywords='azure django',

sql_server/pyodbc/base.py

@@ -19,8 +19,8 @@
 from django.utils.version import get_version_tuple
 
 pyodbc_ver = get_version_tuple(Database.version)
-if pyodbc_ver < (4,0):
-    raise ImproperlyConfigured("pyodbc 4.0 or newer is required; you have %s" % Database.version)
+if pyodbc_ver < (3,0):
+    raise ImproperlyConfigured("pyodbc 3.0 or newer is required; you have %s" % Database.version)
 
 from django.conf import settings
 from django.db import NotSupportedError