fix #1328 and #720
Type: bug
The following has been addressed in the PR:
Instead of returning a 404 (Not Found) when npm, yarn, etc requests a package and the package cannot be acquired from an uplink due to a connection timeout, socket timeout, or connection reset problem, a 503 (service unavailable) is returned by Verdaccio instead. In limited testing of a few versions of npm and yarn, both of these clients correctly attempt to retry the request when a 503 is returned.
Added functional tests to verify the behavior (this adds a dev dependency on nock, which provides HTTP request mocking
Description:
This resolves issue #1328 and #720, and ensures npm/yarn install commands don't fail immediately when there is an intermittent network timeout problem with an uplink. Instead Verdaccio will appropriately respond to the client with a 503. A 404 response (current behavior) incorrectly tells the client that the package does not exist (which may or may not be true) and to not try again.
