More randomness in workers

Change-Id: I82154491576fa724d87ef30668f015f1c58fa93a
Reviewed-on: https://gerrit.spotify.net/gerrit/34115
TC-Compile-And-Test: teamcity teamcity <teamcity@spotify.com>
Reviewed-by: Erik Bernhardsson <erikbern@spotify.com>
Refactored notification emails. Crashes in complete() doesn't abort the entire scheduling process anymore.

Change-Id: I40f7a30bdf34fecbc6457f6911942b36e48997be
Reviewed-on: https://gerrit.spotify.net/gerrit/34538
TC-Compile-And-Test: teamcity teamcity <teamcity@spotify.com>
Reviewed-by: Anders Nyman <nyman@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>
Allowing non-boolean returns from the complete method. This should fix endsongsource and a few other sources

Change-Id: I31d8ef1161534c8f03c9fffb92afa391d0d0ea7c
Reviewed-on: https://gerrit.spotify.net/gerrit/34698
Reviewed-by: Anders Nyman <nyman@spotify.com>
Commented out broken test

Change-Id: Ib3f6242b5ecce61f4754090667776c423a22228a
Reviewed-on: https://gerrit.spotify.net/gerrit/34699
TC-Compile-And-Test: teamcity teamcity <teamcity@spotify.com>
Reviewed-by: Anders Nyman <nyman@spotify.com>
Adding dummy __enter__ method should hopefully fix a Python 2.7 problem

Change-Id: If28b1e41ceb2e95f770c5c7c226da93c9ea3d156
Reviewed-on: https://gerrit.spotify.net/gerrit/34887
TC-Compile-And-Test: teamcity teamcity <teamcity@spotify.com>
Reviewed-by: Erik Bernhardsson <erikbern@spotify.com>
Fixed problem in previous commit (sorry, forgot that the HDFS tests are not run automatically)

Change-Id: Id4363d7ac0d7de45ac16e80b7ef9d7f133f6dbef