Changed cell_methods regex slightly to fix failures in unit tests.

Also added new unit test to check cell_methods with:
  1. Name only (no colon and method)
  2. Not space between colon separator and method.

Author: ukmo-ccbunney

lib/iris/fileformats/_nc_load_rules/helpers.py

@@ -202,11 +202,11 @@
 _CM_INTERVAL = "interval"
 _CM_METHOD = "method"
 _CM_NAME = "name"
-_CM_PARSE_NAME = re.compile(r"([\w_]+\s*?:\s?)+")
+_CM_PARSE_NAME = re.compile(r"([\w_]+\s*?:\s*)+")
 _CM_PARSE = re.compile(
     r"""
-                           (?P<name>([\w_]+\s*?:\s?)+)
-                           (?P<method>[\w_\s]+(?![\w_]*\s*?:))\s*
+                           (?P<name>([\w_]+\s*?:\s*)+)
+                           (?P<method>[^\s][\w_\s]+(?![\w_]*\s*?:))\s*
                            (?:
                                \(\s*
                                (?P<extra>.+)

lib/iris/tests/unit/fileformats/nc_load_rules/helpers/test_parse_cell_methods.py

@@ -19,6 +19,7 @@ class Test(tests.IrisTest):
     def test_simple(self):
         cell_method_strings = [
             "time: mean",
+            "time:mean",
             "time : mean",
         ]
         expected = (CellMethod(method="mean", coords="time"),)
@@ -125,6 +126,7 @@ def test_badly_formatted_warning(self):
         cell_method_strings = [
             # "time: maximum (interval: 1 hr comment: first bit "
             # "time: mean (interval: 1 day comment: second bit)",
+            'time',
             "time: (interval: 1 hr comment: first bit) "
             "time: mean (interval: 1 day comment: second bit)",
             "time: maximum (interval: 1 hr comment: first bit) "