To reproduce:
1. Open projects attached, scene scene
2. Press play - no errors
3. In Hierarchy window, select Video Player
4. In Inspector window, Video Player component, URL variable, input any string and press play

Expected: single error appears in console
Actual: two errors appear in console

Reproduced in: 5.6.1p4, 2017.1.0b10, 2017.2.0a4

Notes: "can't play movie []" also appears any time VideoPlayer.url value is changed, probably intended, but is slightly misleading as error usually pops up when VideoPlayer.Play() method is called through any means
Notes: another thing is that "Can't play movie[]" do not appear when URL is empty - if editor is trying to be mistake-proof, why empty URL is an exception?
Notes: VideoPlayer did not exist in earlier versions