Fix SSL certificate verification issue

[kunaltyagi]

Detected while using rosdep (ros-infrastructure/rosdep#808)

[kunaltyagi]

Post the changes in linked PR, the errors detected are:

#7 37.97 Wrote /etc/ros/rosdep/sources.list.d/20-default.list
#7 37.97 Recommended: please run
#7 37.97 
#7 37.97        rosdep update
#7 37.97 
#7 69.46 Warning: running 'rosdep update' as root is not recommended.
#7 69.46   You should run 'sudo rosdep fix-permissions' and invoke 'rosdep update' again without sudo.
#7 69.46 ERROR: error loading sources list:
#7 69.46        <urlopen error <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1056)> (https://raw.githubusercontent.com/ros/rosdistro/master/index-v4.yaml)>
#7 69.46 reading in sources list data from /etc/ros/rosdep/sources.list.d
#7 69.46 Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/osx-homebrew.yaml
#7 69.46 Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/base.yaml
#7 69.46 Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
#7 69.46 Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml
#7 69.46 Hit https://raw.githubusercontent.com/ros/rosdistro/master/releases/fuerte.yaml
#7 69.46 Query rosdistro index https://raw.githubusercontent.com/ros/rosdistro/master/index-v4.yaml
------

Investigation pointed to a urlopen without a SSL context from rosdistro

[kunaltyagi]

Sole CI error is for Python 3.5 which is EOL

[cottsay]

PEP 476 states that the default Python behavior is to use the system default certificate database. Manually supplying the context to use certifi, which explicitly states that it is the Mozilla collection, overrides that behavior.

The problem isn't that a context isn't provided, it's that your system's default certificate database isn't able to verify the connection, but Mozilla's database is.

I'm moderately confident that this is a problem with your system configuration.

[kunaltyagi]

This is an issue with the distro, so can't really keep this open