Resolve the pesky "website may be down" errors during rosdep {init, update}

[kunaltyagi]

New desciption

While trying to recreate the env for bad networks, I found an pesky issue in rosdep init. This PR resolves that but not the handshake time-out issue.

Old description

On some networks, the following error is observed:

Hit https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
ERROR: unable to process source [https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml]:
        <urlopen error ('_ssl.c:711: The handshake operation timed out',)> (https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml)

This PR resolves the issue by trying the connection multiple times. Increasing timeout was tried but did not always succeed.

Followup from #687

@nuclearsandwich Would it be possible to have a test env for this?

[kunaltyagi]

Failing tests (test_rosdep_sources_list):

• test_SourcesListLoader_create_default
• test_load_cached_sources_list

The failure messages look alright to me (bad host name not found). Will try reverting the whitespace change

EDIT: rewrote the change instead of relying on git merge. All tests passing now

[codecov-commenter]

Codecov Report

Merging #808 (3b330b3) into master (30a25a7) will decrease coverage by 0.89%.
The diff coverage is 62.50%.

@@            Coverage Diff             @@
##           master     #808      +/-   ##
==========================================
- Coverage   74.96%   74.06%   -0.90%     
==========================================
  Files          42       42              
  Lines        3283     3285       +2     
==========================================
- Hits         2461     2433      -28     
- Misses        822      852      +30     

Impacted Files	Coverage Δ
src/rosdep2/main.py	47.67% <0.00%> (-1.17%)	⬇️
src/rosdep2/sources_list.py	85.15% <56.00%> (-1.44%)	⬇️
src/rosdep2/gbpdistro_support.py	93.69% <100.00%> (-1.72%)	⬇️
src/rosdep2/rep3.py	93.33% <100.00%> (-6.67%)	⬇️
src/rosdep2/shell_utils.py	93.18% <0.00%> (-6.82%)	⬇️
src/rosdep2/meta.py	96.07% <0.00%> (-3.93%)	⬇️
src/rosdep2/platforms/osx.py	48.61% <0.00%> (-3.32%)	⬇️
src/rosdep2/platforms/source.py	88.26% <0.00%> (-2.29%)	⬇️
... and 1 more

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