Redo ANSI support detection

When using nose to directly run the test suite it 'steals' stdout per
default. This causes the old implementation of ANSI detection to error
as stdout does not have a fileno function anymore.

pelican/log.py

@@ -172,8 +172,26 @@ class LimitLogger(SafeLogger):
 logging.setLoggerClass(LimitLogger)
 
 
+def supports_color():
+    """
+    Returns True if the running system's terminal supports color,
+    and False otherwise.
+
+    from django.core.management.color
+    """
+    plat = sys.platform
+    supported_platform = plat != 'Pocket PC' and \
+        (plat != 'win32' or 'ANSICON' in os.environ)
+
+    # isatty is not always implemented, #6223.
+    is_a_tty = hasattr(sys.stdout, 'isatty') and sys.stdout.isatty()
+    if not supported_platform or not is_a_tty:
+        return False
+    return True
+
+
 def get_formatter():
-    if os.isatty(sys.stdout.fileno()) and not sys.platform.startswith('win'):
+    if supports_color():
         return ANSIFormatter()
     else:
         return TextFormatter()