Enable flake8 checks

This commit enables new flake8 checks:
* E265  block comment should start with '# '
* H405  multi line docstring summary not separated with an empty line
* E123  closing bracket does not match indentation of opening bracket's line
* H238  old style class declaration, use new style (inherit from `object`)
* E128  continuation line under-indented for visual indent
and makes related changes in the code.

Change-Id: Ie993afc930f6b74d7a990bcaa9fc0e9f5ba1585c

glanceclient/__init__.py

@@ -12,7 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-#NOTE(bcwaldon): this try/except block is needed to run setup.py due to
+# NOTE(bcwaldon): this try/except block is needed to run setup.py due to
 # its need to import local code before installing required dependencies
 try:
     import glanceclient.client