Run shared tests from both v3 and v4 of juggler

[bajtos]

At the moment, our connectors are installing juggler 3.x to run the test suite. When we make a change to juggler@3, cis-jenkins detects downstream dependency and triggers CI build of connectors with the modified juggler version. When we make a change to juggler's master, no downstream builds are triggered.

In the past, we were maintaining multiple branches to test connectors against different juggler versions. E.g. loopback-2.x containing code from "master" but installing juggler 2.x for testing. This is rather impractical, because we don't have bandwidth to update those other branches with changes made to master.

In this pull request, I am reworking connector test setup to execute tests from both juggler versions 3.x and 4.x.

Checklist

• New tests added or existing tests modified to cover all changes
• Code conforms with the style
  guide

[bajtos]

Please note the test failures are coming from juggler v4, we haven't been running those tests yet. I'll fix them before landing this PR if we decide to continue in this direction.

[bajtos]

Please note the test failures are coming from juggler v4, we haven't been running those tests yet. I'll fix them before landing this PR if we decide to continue in this direction.

Should be fixed now, via loopbackio/loopback-datasource-juggler#1733 and loopback-datasource-juggler@4.6.4

[bajtos]

loopback-connector-postgresql/node=6.x,os=windows — Failed! (795e064)

This test sometimes passes and other times it fails and the error message is not clear about what went wrong :(

115 passing (6s)
  1 failing

D:\t\t4938861194367131829dirbfr\node_modules\build-framework\node_modules\mocha-jenkins-reporter\lib\jenkins.js:259
    var n = ++currentSuite.failures;
                          ^

TypeError: Cannot read property 'failures' of null
    at Runner.<anonymous> (D:\t\t4938861194367131829dirbfr\node_modules\build-framework\node_modules\mocha-jenkins-reporter\lib\jenkins.js:259:27)
    at emitTwo (events.js:111:20)
    at Runner.emit (events.js:191:7)
    at Runner.fail (D:\workspace\loopback-connector-postgresql\d60c4a15\node_modules\mocha\lib\runner.js:251:8)
    at Runner.uncaught (D:\workspace\loopback-connector-postgresql\d60c4a15\node_modules\mocha\lib\runner.js:757:8)
    at process.uncaught (D:\workspace\loopback-connector-postgresql\d60c4a15\node_modules\mocha\lib\runner.js:839:10)
    at emitOne (events.js:96:13)
    at process.emit (events.js:188:7)
    at process._fatalException (bootstrap_node.js:300:26)

The CI re-runs the tests with DEBUG logs enabled and then the test suite passes. I am proposing to ignore this problem for now. Node.js 6 has reached EOL few days ago, I think it's time to remove it from our CI platforms.

[cis-jenkins] x64 && linux && nvm && dbs,8 — Failed! (795e064)

I suspect this is intermittent too, I've seen this error few times on my machine too, but not always.

09:20:45   1) autoupdate
09:20:45        foreign key constraint
09:20:45          should create, update, and delete foreign keys:
09:20:45 
09:20:45       Uncaught AssertionError [ERR_ASSERTION]: error: duplicate key value violates unique constraint "pg_namespace_nspname_index"
09:20:45       + expected - actual
09:20:45 
09:20:45       -false
09:20:45       +true
09:20:45       
09:20:45       at /home/jenkins/workspace/nb/loopback-connector-postgresql~master/3ed5ebba/test/postgresql.autoupdate.test.js:632:9

[bajtos]

@slnode test please

[bajtos]

All checks have passed this time. This pull request is ready for final review & landing. (I'll clean up the git history before merging.)

[b-admike]

LGTM, hopefully we can see the changes in action soon.