Fix track-features when there is no package with feature yet.

When solving dependencies and listing the installed features, it was
being considered only features present on field "features" and not on
"track-features".

conda/resolve.py

@@ -694,7 +694,7 @@ def installed_features(self, installed):
         res = set()
         for fn in installed:
             try:
-                res.update(self.features(fn))
+                res.update(self.track_features(fn))
             except KeyError:
                 pass
         return res

tests/test_resolve.py

@@ -946,6 +946,32 @@ def test_nonexistent_deps():
         'zlib-1.2.7-0.tar.bz2',
     ]
 
+
+def test_install_package_with_feature():
+    index2 = index.copy()
+    index2['mypackage-1.0-featurepy33_0.tar.bz2'] = {
+        'build': 'featurepy33_0',
+        'build_number': 0,
+        'depends': ['python 3.3*'],
+        'name': 'mypackage',
+        'version': '1.0',
+        'features': 'feature',
+    }
+    index2['feature-1.0-py33_0.tar.bz2'] = {
+        'build': 'py33_0',
+        'build_number': 0,
+        'depends': ['python 3.3*'],
+        'name': 'mypackage',
+        'version': '1.0',
+        'track_features': 'feature',
+    }
+
+    r = Resolve(index2)
+
+    # It should not raise
+    r.solve(['mypackage'], installed=['feature-1.0-py33_0.tar.bz2'])
+
+
 def test_circular_dependencies():
     index2 = index.copy()
     index2['package1-1.0-0.tar.bz2'] = {