change older conda-build ver to 2.0.*; comment on metadata obj collec…

…tion

.travis.yml

@@ -14,8 +14,9 @@ env:
     matrix:
         - PYTHON=2.7
         - PYTHON=3.4
+        # test against older conda-build
         - PYTHON=3.5
-          EXTRA_DEPS='conda-build=2.1.*'
+          EXTRA_DEPS='conda-build=2.0.*'
         - PYTHON=3.5
           CONDA_BUILD_ALL_TEST_ANACONDA_CLOUD=1
         - PYTHON=3.5

conda_build_all/builder.py

@@ -87,8 +87,12 @@ def list_metas(directory, max_depth=0, config=None):
             if hasattr(conda_build, 'api'):
                 pkgs = conda_build.api.render(new_root, config=config,
                                         finalize=False, bypass_env_check=True)
+                # cb2 returns a tuple, with the metadata object as the first
+                #    element.  That's all we care about.
                 if hasattr(pkgs[0], 'config'):
                     pkgs = [pkgs[0]]
+                # cb3 returns a list of tuples, each with the metadata object
+                #    as the first element.  Collect them up.
                 else:
                     pkgs = [pkg[0] for pkg in pkgs]
                 packages.extend(pkgs)