vga.pcf:15: fatal error: no set_io constraints for pin `clr'

[felipesanches]

Trying to build the example I got this:

2.25. Executing CHECK pass (checking for obvious problems).
checking module vga..
found and reported 0 problems.

2.26. Executing BLIF backend.

End of script. Logfile hash: c7ef1d2f2d
CPU: user 0.76s system 0.04s, MEM: 43.52 MB total, 14.25 MB resident
Yosys 0.5+426 (git sha1 8b3f8cd, clang 3.8.0-2ubuntu4 -fPIC -Os)
Time spent: 18% 25x opt_const (0 sec), 16% 23x opt_share (0 sec), ...
seed: 1
device: 1k
read_chipdb +/share/arachne-pnr/chipdb-1k.bin...
  supported packages: cb121, cb132, cb81, cm121, cm36, cm49, cm81, qn84, swg16tr, tq144, vq100
read_blif vga.blif...
prune...
read_pcf vga.pcf...
vga.pcf:15: fatal error: no set_io constraints for pin `clr'