URL dependencies are not included in lambda dist

[Haapalaj]

When adding and URL dependency to project as runtime dependency, e.g.
in build.py init phase: project.depends_on(modulename, url="file://" + .tar.gz)
so it is expected to be installed to target/lambda_dependencies dir, but this won't work.

It seems that in lambda_tasks.prepare_dependencies_dir the dependencies
are fetch by build_install_dependencies_string(project).
and the build_install_dependencies_string(project) excludes URL dependencies.

How this should be resolved, either to workaround build_install_dependencies_string in lambda_tasks
or modify the actual build_install_dependencies_string?

We resolved this by adding additional function to our build which installs all URL dependencies:

def include_url_dependencies(project, logger, target_directory):
    """ Installs url dependencies to target_directory.  """
    dependencies = [
        dependency for dependency in project.dependencies if dependency.url]
    if not dependencies:
        return ""

    pip_cmd = 'pip install --target {0} {1}'
    for dependency in dependencies:

        cmd = pip_cmd.format(target_directory, dependency.url)
        logger.info("Installing url-dependency {0}: '{1}'".format(dependency.url, cmd))

        process = subprocess.Popen(cmd.split(), stdout=subprocess.PIPE)
        process.communicate()
        if process.returncode != 0:
            msg = "Command '{0}' failed to install dependency: {1}".format(
                    cmd, process.returncode)
            raise Exception(msg)

[esc]

Sure, please provide a pull-request and this may get merged.