Custom SSL handling was introduced because disabling SSL layer compression
provided an approximately five fold performance increase in some
cases. Without SSL layer compression disabled the image transfer would be
CPU bound -- with the CPU performing the DEFLATE algorithm.  This would
typically limit image transfers to < 20 MB/s. When --no-ssl-compression
was specified the client would not negotiate any compression algorithm
during the SSL handshake with the server which would remove the CPU
bottleneck and transfers could approach wire speed.

In order to support '--no-ssl-compression' two totally separate code
paths exist depending on whether this is True or False.  When SSL
compression is disabled, rather than using the standard 'requests'
library, we enter some custom code based on pyopenssl and httplib in
order to disable compression.

This patch/spec proposes removing the custom code because:

* It is a burden to maintain

 Eg adding new code such as keystone session support is more complicated

* It can introduce additional failure modes

 We have seen some bugs related to the 'custom' certificate checking

* Newer Operating Systems disable SSL for us.

 Eg. While Debian 7 defaulted to compression 'on', Debian 8 has compression
 'off'. This makes both servers and client less likely to have compression
 enabled.

* Newer combinations of 'requests' and 'python' do this for us

 Requests disables compression when backed by a version of python which
 supports it (>= 2.7.9). This makes clients more likely to disable
 compression out-of-the-box.

* It is (in principle) possible to do this on older versions too

 If pyopenssl, ndg-httpsclient and pyasn1 are installed on older
 operating system/python combinations, the requests library should
 disable SSL compression on the client side.

* Systems that have SSL compression enabled may be vulnerable to the CRIME
(https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2012-4929) attack.
Installations which are security conscious should be running the Glance
server with SSL disabled.

Full Spec: https://review.openstack.org/#/c/187674
Blueprint: remove-custom-client-ssl-handling

Change-Id: I7e7761fc91b0d6da03939374eeedd809534f6edf

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

In common.http.py, the exception RequestTimeout has
wrong message.This patch fixed it.

Change-Id: Ie8ff188b9c82ce424cb8177278f36e4d1275b306

To make this work we create a different HTTPClient that extends the
basic keystoneclient Adapter. The Adapter is a standard set of
parameters that all clients should know how to use like region_name and
user_agent. We extend this with the glance specific response
manipulation like loading and sending iterables.

Implements: bp session-objects
Change-Id: Ie8eb4bbf7d1a037099a6d4b272cab70525fbfc85

This patch moves the glanceclient unit tests to the standard directory
(xxxclient/tests/unit) in preparation for adding functional gate tests
'check-glanceclient-dsvm-functional' in the same vein as existing client
tests for other projects, eg:

* check-novaclient-dsvm-functional
* check-keystoneclient-dsvm-functional
* check-neutronclient-dsvm-functional

Change-Id: I29d4b9e3a428c851575ee9afde40d6df583456c4