Updates to run and pass flake8-builtins (#974)

There are flake8-builtins violations which appear as part of rosdep's
public API. We'll supporess those to avoid breaking API, but still add
the linter plugin so we don't regress more.

setup.py

@@ -17,6 +17,7 @@
     'extras_require': {
         'test': [
             'flake8',
+            'flake8-builtins',
             'flake8-comprehensions',
             'pytest',
         ],

src/rosdep2/meta.py

@@ -88,7 +88,7 @@ def __init__(self, cache_dir=None):
         self._cache_dir = cache_dir
         self._loaded = {}
 
-    def set(self, category, metadata):
+    def set(self, category, metadata):  # noqa: A003
         """Add or overwrite metadata in the cache."""
         wrapper = CacheWrapper(category, metadata)
         # print(category, metadata)

src/rosdep2/sources_list.py

@@ -229,8 +229,8 @@ def __str__(self):
     def __repr__(self):
         return repr((self.type, self.url, self.tags, self.rosdep_data, self.origin))
 
-    @property
-    def type(self):
+    @property  # noqa: A003
+    def type(self):  # noqa: A003
         """
         :returns: data source type
         """