Error tty in gpg2

[ElaadF]

Step 20/41 : RUN gpg2 --keyserver hkp://keys.gnupg.net --recv-key CD9C0E09B0C780943A1AD85553F8BD99F40DCB31
 ---> Running in 97bf3b1092e6
gpg: directory '/root/.gnupg' created
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: cannot open '/dev/tty': No such device or address
The command '/bin/sh -c gpg2 --keyserver hkp://keys.gnupg.net --recv-key CD9C0E09B0C780943A1AD85553F8BD99F40DCB31' returned a non-zero code: 2

It seems that some times this error appear randomly when I build the image. The only way, I find, to fix this, is to re-run the command...weird...

[gimau]

I have the same problem, but it never works for me. Do you have an idea ?