fix handling of single strings passed to vCategory

CHANGES.rst

@@ -20,6 +20,9 @@ New features:
 
 Bug fixes:
 
+- CATEGORIES field now accepts a string as argument
+  Ref: #322
+  [jacadzaca]
 - Multivalue FREEBUSY property is now parsed properly
   Ref: #27
   [jacadzaca]

src/icalendar/prop.py

@@ -261,7 +261,7 @@ def from_ical(ical, timezone=None):
 class vCategory:
 
     def __init__(self, c_list):
-        if not hasattr(c_list, '__iter__'):
+        if not hasattr(c_list, '__iter__') or isinstance(c_list, str):
             c_list = [c_list]
         self.cats = [vText(c) for c in c_list]
 

src/icalendar/tests/calendars/issue_322_expected_calendar.ics

@@ -0,0 +1,6 @@
+BEGIN:VCALENDAR
+BEGIN:VEVENT
+SUMMARY:Event with bare string as argument for categories
+CATEGORIES:Lecture
+END:VEVENT
+END:VCALENDAR

src/icalendar/tests/test_issue_322_single_strings_characters_split_into_multiple_categories.py

@@ -0,0 +1,10 @@
+from icalendar import Calendar, Event
+
+
+def test_issue_322_single_string_split_into_multiple_categories(calendars):
+    calendar = Calendar()
+    event = Event()
+    event.add('summary', 'Event with bare string as argument for categories')
+    event.add('categories', "Lecture")
+    calendar.add_component(event)
+    assert calendar.to_ical() == calendars.issue_322_expected_calendar.raw_ics