Use snapshot of rosdep list on melodic

After ros/rosdistro#39174 was merged, rosdep key 'python-omniorb' cannot be resolved on melodic

rosdep_snapshots/30-bionic.list

@@ -0,0 +1,12 @@
+# This list targets a snapshot of rosdistro (before https://github.com/ros/rosdistro/pull/39174 was merged) for post-EOL use on Bionic
+
+# os-specific listings first
+yaml https://raw.githubusercontent.com/ros/rosdistro/e0a9ff920317daff3b6f177e1325e27f498063c1/rosdep/osx-homebrew.yaml osx
+
+# generic
+yaml https://raw.githubusercontent.com/ros/rosdistro/e0a9ff920317daff3b6f177e1325e27f498063c1/rosdep/base.yaml
+yaml https://raw.githubusercontent.com/ros/rosdistro/e0a9ff920317daff3b6f177e1325e27f498063c1/rosdep/python.yaml
+yaml https://raw.githubusercontent.com/ros/rosdistro/e0a9ff920317daff3b6f177e1325e27f498063c1/rosdep/ruby.yaml
+gbpdistro https://raw.githubusercontent.com/ros/rosdistro/e0a9ff920317daff3b6f177e1325e27f498063c1/releases/fuerte.yaml fuerte
+
+# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

travis.sh

@@ -297,6 +297,9 @@ fi
 if [[ "$ROS_DISTRO" =~ "hydro"|"indigo"|"jade"|"kinetic"|"lunar" ]]; then
     sudo rm /etc/ros/rosdep/sources.list.d/20-default.list
     sudo cp $(dirname "${BASH_SOURCE[0]}")/rosdep_snapshots/30-xenial.list /etc/ros/rosdep/sources.list.d
+elif [[ "$ROS_DISTRO" == "melodic" ]]; then
+    sudo rm /etc/ros/rosdep/sources.list.d/20-default.list
+    sudo cp $(dirname "${BASH_SOURCE[0]}")/rosdep_snapshots/30-bionic.list /etc/ros/rosdep/sources.list.d
 fi
 ret=1
 rosdep update --include-eol-distros|| while [ $ret != 0 ]; do sleep 1; rosdep update --include-eol-distros && ret=0 || echo "failed"; done