Can't intall python dependencies in ROS 2

[ghost]

This is related to #519 and #542

I get the following error when trying to install a python dependency using rosdep in a Dashing release.

ERROR: Rosdep experienced an internal error.
Please go to the rosdep page [1] and file a bug report with the message below.
[1] : http://www.ros.org/wiki/rosdep
rosdep version: 0.15.1
Bad installer [pip]: [Errno 2] No such file or directory: 'pip': 'pip'

Since the default ROS 2 installation uses python3, we need rosdep to install the packages using pip3, however there is no way to specify that.

You can see a failing build log here:
https://travis-ci.org/ros-planning/navigation2/builds/531898111?utm_source=github_status&utm_medium=notification

[russkel]

I discovered that using pipenv can alleviate some of these issues. It symlinks a pip and isolates the packages from the system.

[sloretz]

I think this is fixed by #709. Would you mind checking using rosdep >=0.17.0?

[ghost]

I can no longer reproduce the problem. Looks like it is fixed. Thanks!