Fixes #469 - Prevented rst crash with only-space strings (#470)

Thanks nexone for the report.

HISTORY.md

@@ -1,5 +1,11 @@
 # History
 
+## Unreleased
+
+### Bugfixes
+
+- Prevented crash in rst export with only-space strings (#469).
+
 ## 2.0.0 (2020-05-16)
 
 ### Breaking changes

src/tablib/formats/_rst.py

@@ -24,7 +24,7 @@ def _max_word_len(text):
     >>> _max_word_len('Python Module for Tabular Datasets')
     8
     """
-    return max(len(word) for word in text.split()) if text else 0
+    return max([len(word) for word in text.split()], default=0) if text else 0
 
 
 class ReSTFormat:

tests/test_tablib.py

@@ -659,6 +659,7 @@ class RSTTests(BaseTestCase):
         data.headers = self.headers
         data.append(self.john)
         data.append(('Wendy', '', 43))
+        data.append(('Esther', ' ', 31))
         self.assertEqual(
             data.export('rst'),
             '==========  =========  ===\n'
@@ -666,6 +667,7 @@ class RSTTests(BaseTestCase):
             '==========  =========  ===\n'
             'John        Adams      90 \n'
             'Wendy                  43 \n'
+            'Esther                 31 \n'
             '==========  =========  ==='
         )