Handle printing bounds of long time interval coords (SciTools#3140)

* Handle printing time bounds

* Whatsnew, whitespace fix for test result

docs/iris/src/whatsnew/contributions_2.2.0/bugfix_2018-Aug-20_print-long-time-interval-bounds.txt

@@ -0,0 +1,2 @@
+* Fixed a bug that prevented printing time coordinates with bounds when the time
+  coordinate was measured on a long interval (that is, ``months`` or ``years``).

lib/iris/coords.py

@@ -782,7 +782,11 @@ def __str__(self):
                 points = self._str_dates(self.points)
             bounds = ''
             if self.has_bounds():
-                bounds = ', bounds=' + self._str_dates(self.bounds)
+                if self.units.is_long_time_interval():
+                    bounds_vals = self.bounds
+                else:
+                    bounds_vals = self._str_dates(self.bounds)
+                bounds = ', bounds={vals}'.format(vals=bounds_vals)
             result = fmt.format(self=self, cls=type(self).__name__,
                                 points=points, bounds=bounds,
                                 other_metadata=self._repr_other_metadata())

lib/iris/tests/unit/coords/test_Coord.py

@@ -677,13 +677,33 @@ def test_short_time_interval(self):
         result = coord.__str__()
         self.assertEqual(expected, result)
 
+    def test_short_time_interval__bounded(self):
+        coord = DimCoord([5, 6], standard_name='time',
+                         units='days since 1970-01-01')
+        coord.guess_bounds()
+        expected = ("DimCoord([1970-01-06 00:00:00, 1970-01-07 00:00:00], "
+                    "bounds=[[1970-01-05 12:00:00, 1970-01-06 12:00:00],\n"
+                    "       [1970-01-06 12:00:00, 1970-01-07 12:00:00]], "
+                    "standard_name='time', calendar='gregorian')")
+        result = coord.__str__()
+        self.assertEqual(expected, result)
+
     def test_long_time_interval(self):
         coord = DimCoord([5], standard_name='time',
                          units='years since 1970-01-01')
         expected = "DimCoord([5], standard_name='time', calendar='gregorian')"
         result = coord.__str__()
         self.assertEqual(expected, result)
 
+    def test_long_time_interval__bounded(self):
+        coord = DimCoord([5, 6], standard_name='time',
+                         units='years since 1970-01-01')
+        coord.guess_bounds()
+        expected = ("DimCoord([5 6], bounds=[[4.5 5.5]\n [5.5 6.5]], "
+                    "standard_name='time', calendar='gregorian')")
+        result = coord.__str__()
+        self.assertEqual(expected, result)
+
     def test_non_time_unit(self):
         coord = DimCoord([1.])
         expected = repr(coord)