Handle version exclusion constraint

Handle gem version exclusion from gemspec ( != symbol )

/reviewed-by @kirr
/reviewed-on !6

rubygems.py

@@ -49,8 +49,8 @@ class Recipe(object):
 
         deployment = options.get('deployment')
         self.deployment = is_true(deployment) if deployment else not allow_picked_versions()
-        self.gem_regex = re.compile(r'\s+([\w\-_.]+) \((<|~>|>=) '
-                                    r'((\d+\.)*\d+)(, (<|~>|>=) ((\d+\.)*\d+))?\)')
+        self.gem_regex = re.compile(r'\s+([\w\-_.]+) \((<|~>|>=|!=) '
+                                    r'((\d+\.)*\d+)(, (<|~>|>=|!=) ((\d+\.)*\d+))?\)')
 
     def run(self, cmd, environ=None):
         """Run the given ``cmd`` in a child process."""
@@ -109,6 +109,9 @@ class Recipe(object):
         elif cons_dict['symbol'] == '>=':
             if dep_version_list >= cons_version_list:
                 return
+        elif cons_dict['symbol'] == '!=':
+            if dep_version_list != cons_version_list:
+                return
         else:
             raise ValueError(
                 'Unhandled symbol in constraint %s for dependecy %s of gem %s'

tests/test_data/dependency_sass-1.0.0.txt

+Gem sass-1.0.0
+  hashie (>= 0.3.0, != 1.0.0)
+

tests/test_rubygems.py

@@ -482,3 +482,23 @@ class RubyGemsDeploymentTestCase(RubyGemsTestCase):
     def test_deployment_similar_second_constraint_success(
             self, path, patches, buildout, name, options, version):
         self.deployment_install_test(buildout, name, path, patches, options, version)
+  
+    @deployment_fixture({'recipe': {
+        'gems': 'hashie==1.0.0 sass==1.0.0'
+    }})
+    def test_deployment_version_exclusion_constraint_error(
+            self, path, patches, buildout, name, options, version):
+        recipe = rubygems.Recipe(buildout, name, options)
+        self.assertRaisesRegexp(
+            zc.buildout.UserError,
+            'Configuration error, version 1.0.0 for gem hashie '
+            'does not satisfy dependency constraint != 1.0.0 of gem sass',
+            recipe.install
+        )
+
+    @deployment_fixture({'recipe': {
+        'gems': 'hashie==0.3.1 sass==1.0.0'
+    }})
+    def test_deployment_version_exclusion_constraint_success(
+            self, path, patches, buildout, name, options, version):
+        self.deployment_install_test(buildout, name, path, patches, options, version)