Fix merged into upstream master: https://github.com/ClusterLabs/pcs/commit/095113b23216cfb65fdd863d3955566ebb64a79c

ENVIRONMENT PREPARATION:
- a 2 node cluster with nodes: node1, node2
- a dummy resource (pcs resource create dummy ocf:heartbeat:Dummy)

To test this fix, run commands:
# pcs constraint location dummy prefers node1 node2=invalid
# echo $?
1
# pcs constraint location show 
Location Constraints:

# pcs constraint location dummy avoids node1=-50 node2
# echo $?
0
# pcs constraint location show 
Location Constraints:
  Resource: dummy
    Enabled on: node1 (score:50)
    Disabled on: node2 (score:-INFINITY)

After fix:

[root@r81-node-01 ~]# rpm -q pcs
pcs-0.10.3-1.el8.x86_64

[root@r81-node-01 pcs]# pcs constraint location d-01 prefers r81-node-01 r81-node-02=invalid
Error: invalid score 'invalid', use integer or INFINITY or -INFINITY
[root@r81-node-01 pcs]# echo $?
1
[root@r81-node-01 pcs]# pcs constraint location d-01 avoids r81-node-01=-50 r81-node-02
[root@r81-node-01 pcs]# echo $?
0
[root@r81-node-01 pcs]# pcs constraint
Location Constraints:
  Resource: d-01
    Enabled on:
      Node: r81-node-01 (score:50)
    Disabled on:
      Node: r81-node-02 (score:-INFINITY)
Ordering Constraints:
Colocation Constraints:
Ticket Constraints:

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2020:1568