Fix Travis

[lrapetti]

Fix #124 (comment).
As discussed in #121 (comment) the support for Ubuntu 16.04 is removed.

[lrapetti]

The MacOs test is failing to download ipopt:

...
==> Downloading https://www.coin-or.org/download/source/Ipopt/Ipopt-3.12.9.tgz
curl: (7) Failed to connect to www.coin-or.org port 443: Operation timed out
Error: An exception occurred within a child process:
  DownloadError: Failed to download resource "ipopt"
Download failed: https://www.coin-or.org/download/source/Ipopt/Ipopt-3.12.9.tgz
The command "brew install eigen ace tinyxml gsl dartsim/dart/ipopt qt" failed and exited with 1 during .
Your build has been stopped.

I don't know if it is a temporary problem with the server. I will try to relaunch the tests again later.

[traversaro]

I guess it is a temporary down of the coin-or.org website as an whole, see https://downforeveryoneorjustme.com/coin-or.org . However, recently ipopt moved its infrastructure to github, so it could make sense to modify the homebrew formula to point to github's tarballs and repository.

[lrapetti]

I guess it is a temporary down of the coin-or.org website as an whole, see https://downforeveryoneorjustme.com/coin-or.org . However, recently ipopt moved its infrastructure to github, so it could make sense to modify the homebrew formula to point to github's tarballs and repository.

OK, then I think the CI for MacOS will be broken for the time being. I will procede mergeing the fixies for Ubuntu CI.

[traversaro]

OK, then I think the CI for MacOS will be broken for the time being. I will procede mergeing the fixies for Ubuntu CI.

Note that the problem is that is not only the CI: the installation process itself is currently broken on macOS.
I opened an issue on this at dartsim/homebrew-dart#76 . In theory, it should be sufficient to just change the url and head parameters in https://github.com/dartsim/homebrew-dart/blob/master/Formula/ipopt.rb#L4 to fix the formula, so the fix is not extremely complex.

[lrapetti]

@traversaro actually on Ipopt github they are still pointing to the tarballs at https://www.coin-or.org/download/source/Ipopt/ from which I am currently able to download the files (while I don't see the .tgz in github).

[traversaro]

@traversaro actually on Ipopt github they are still pointing to the tarballs at https://www.coin-or.org/download/source/Ipopt/ from which I am currently able to download the files (while I don't see the .tgz in github).

Cool, then the website is back online. I guess that the .tgz are equivalent to the .tar.gz archives you can find in https://github.com/coin-or/Ipopt/releases . I suspect however that github.com-hosted files should provide a better uptime w.r.t. to coin-or.org tarballs.

For the repo, according to https://list.coin-or.org/pipermail/ipopt/2019-April/004635.html the SVN is not updated anymore, so for sure that needs to be switched.