Fixes #1 by adding Content-Type checking

nbp/table.py

@@ -109,7 +109,9 @@ def download(url):
     try:
         resp = urllib2.urlopen(url)
         if hasattr(resp, 'getcode') and resp.getcode() == 200:
-            return resp
+            if hasattr(resp, 'info') and resp.info()['content-type'] == 'text/xml':
+                return resp
+        return None
     except urllib2.URLError, e:
         resp = None
     return resp

tests.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import nbp
+from datetime import date
 from nose.tools import assert_equals
 
 
@@ -18,3 +19,18 @@ def test_downloads_exchange_rate_properly():
         }
     currency_data = nbp.download_exchange_rate(nbp.date(2010, 7, 11), 'EUR')
     assert_equals(expexted, currency_data)
+
+def test_downloads_exchange_rate_properly_even_with_broken_nbp_404_200():
+    expexted = {
+        'search_date': '2014-11-03',
+        'table_no': u'213/A/NBP/2014',
+        'pub_date': u'2014-11-03',
+        'url': 'http://rss.nbp.pl/kursy/xml2/2014/a/14a213.xml',
+        'currency': {
+            'name': u'euro',
+            'rate': 4.2209,
+            'code': u'EUR',
+            },
+        }
+    currency_data = nbp.download_exchange_rate(date.today(), 'EUR')
+    assert_equals(date.today().strftime('%Y-%m-%d'), currency_data['pub_date'])