It depends on your definition of "no-go zone". It is untrue only if you insist on a extreme definition, e.g. "no outsiders can go in, ever".

It isn't by more normal definitions, e.g. "their non-accessibility by government officials in times of tension", or where taxi drivers fear to go:

http://www.algemeiner.com/2015/12/07/the-truth-about-muslim-no-go-zones-in-europe/#
"Whether or not Molenbeek, Rinkeby, and the Marseilles slum are no-go zones, then, depends on what aspect one chooses to emphasize — their accessibility to ordinary visitors at ordinary times or their inaccessibility to government officials in times of tension. There are also no-go gradations, some places where attacks are more frequent and violent, others less so. However one sums up this complex situation — maybe partial-no-go zones? — they represent a great danger." 

https://www.washingtonpost.com/blogs/erik-wemple/wp/2015/11/16/belgian-ministers-statement-revives-talk-of-no-go-zones/