REP3_TARGETS_URL is hardcoded

[felixf4xu]

Hi,

Currently REP3_TARGETS_URL is hardcoded, as

# location of targets file for processing gbpdistro files
REP3_TARGETS_URL = 'https://raw.githubusercontent.com/ros/rosdistro/master/releases/targets.yaml'

...

if targets_url is None:
    targets_url = REP3_TARGETS_URL
try:
    f = urlopen_gzip(targets_url, timeout=DOWNLOAD_TIMEOUT)

and there is no way to change it when githubusercontent.com is not accessible.

This is not the same case as to FUERTE_GBPDISTRO_URL. It seems that FUERTE_GBPDISTRO_URL is also hardcoded but it's actually not. FUERTE_GBPDISTRO_URL is only used in testing code.

# location of an example gbpdistro file for reference and testing
FUERTE_GBPDISTRO_URL = 'https://raw.githubusercontent.com/ros/rosdistro/' \
    'master/releases/fuerte.yaml'

...

rosdep_data = download_gbpdistro_as_rosdep_data(source.url)

In fact source.url can be changed by editing /etc/ros/rosdep/sources.list.d/20-default.list

I'd like to create a PR and use an env value to change the default value of targets_url, which is similar to ROSDISTRO_INDEX_URL in rosdistro.

Any comment?