Allow comparing of all LooseVersions in Python 3

When a number is in a place where the other version has a letter, the
comparison would fail in Python 3 but succeed in Python 2.
Add patch from https://bugs.python.org/issue14894

easybuild/tools/loose_version.py

@@ -10,6 +10,7 @@
 # - Changes to documentation and formatting
 
 import re
+from itertools import zip_longest
 
 
 class LooseVersion(object):
@@ -48,12 +49,19 @@ def _cmp(self, other):
         if isinstance(other, str):
             other = LooseVersion(other)
 
-        if self.version == other.version:
-            return 0
-        if self.version < other.version:
-            return -1
-        if self.version > other.version:
-            return 1
+        # Modified: Behave the same in Python 2 & 3 when parts are of different types
+        # Taken from https://bugs.python.org/issue14894
+        for i, j in zip_longest(self.version, other.version, fillvalue=''):
+            if not type(i) is type(j):
+                i = str(i)
+                j = str(j)
+            if i == j:
+                continue
+            elif i < j:
+                return -1
+            else:  # i > j
+                return 1
+        return 0
 
     def __eq__(self, other):
         return self._cmp(other) == 0

test/framework/utilities_test.py

@@ -131,6 +131,9 @@ def test_LooseVersion(self):
         self.assertLess(LooseVersion('2.1.5'), LooseVersion('2.2'))
         self.assertLess(LooseVersion('2.1.3'), LooseVersion('3'))
         self.assertLessEqual(LooseVersion('2.1.0'), LooseVersion('2.2'))
+        # Careful here: 1.0 > 1 !!!
+        self.assertGreater(LooseVersion('1.0'), LooseVersion('1'))
+        self.assertLess(LooseVersion('1'), LooseVersion('1.0'))
 
         # The following test is taken from Python disutils tests
         # licensed under the Python Software Foundation License Version 2
@@ -141,7 +144,11 @@ def test_LooseVersion(self):
                     ('3.2.pl0', '3.1.1.6', 1),
                     ('2g6', '11g', -1),
                     ('0.960923', '2.2beta29', -1),
-                    ('1.13++', '5.5.kw', -1))
+                    ('1.13++', '5.5.kw', -1),
+                    # Added from https://bugs.python.org/issue14894
+                    ('a.12.b.c', 'a.b.3', -1),
+                    ('1.0', '1', 1),
+                    ('1', '1.0', -1))
 
         for v1, v2, wanted in versions:
             res = LooseVersion(v1)._cmp(LooseVersion(v2))