Fix enforce crash when matcher functions throw string errors

[Copilot]

• Understand the root cause: err.message concatenation fails when err is a plain string
• Fix CoreEnforcer.lua line 449 to handle both string and table errors
• Fix CoreEnforcer.lua line 494 to handle both string and table errors
• Create test case for keyMatch4 error handling
• Run tests to validate the fix - all 30 tests pass including new keyMatch4 test
• Address code review feedback
• Fix CI benchmark job failure by adding retry logic for luarocks installs

Original prompt

---

This section details on the original issue you should resolve

<issue_title>enforce error</issue_title>
<issue_description>there is a error when use keymatch4 in model.conf

[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = g(r.sub, p.sub) && keyMatch4(r.obj, p.obj) && regexMatch(r.act, p.act)

local Enforcer = require("casbin")

local e = Enforcer:new("/opt/openresty/nginx/conf/lua/casbin/rbac_model.conf", "/opt/openresty/nginx/conf/lua/casbin/examples/rbac_policy.csv")

local cjson = require "cjson"
local response = {}

local sub = "alice" -- the user that wants to access a resource.
local obj = "data1" -- the resource that is going to be accessed.
local act = "read" -- the operation that the user performs on the resource.

if e:enforce(sub, obj, act) then
  response['code'] = 200
  response['result'] = true
  response['msg'] = e:GetPolicy()
  ngx.say(cjson.encode(response))
end

2023/12/12 18:42:33 [error] 208585#0: *4 lua entry thread aborted: runtime error: 
...openresty/luajit/share/lua/5.1/src/main/CoreEnforcer.lua:449: attempt to concatenate field 'message' (a nil value)
stack traceback:
coroutine 0:
        ...openresty/luajit/share/lua/5.1/src/main/CoreEnforcer.lua: in function 'enforceEx'
        ...openresty/luajit/share/lua/5.1/src/main/CoreEnforcer.lua:534: in function 'enforce'

```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes enforce error #154

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[hsluoyz]

@copilot fix: https://github.com/casbin/lua-casbin/actions/runs/21696318490/job/62569433929?pr=169

Run luarocks install lualogging
  luarocks install lualogging
  luarocks install lrexlib-pcre2
  luarocks install luaposix
  luarocks install luasocket
  luarocks install busted
  luarocks install busted-htest
  shell: /usr/bin/bash -e {0}
  env:
    MSYS: winsymlinks:nativestrict
    LUA_PATH: ;;/home/runner/.luarocks/share/lua/5.1/?.lua;/home/runner/.luarocks/share/lua/5.1/?/init.lua;/home/runner/work/lua-casbin/lua-casbin/.luarocks/share/lua/5.1/?.lua;/home/runner/work/lua-casbin/lua-casbin/.luarocks/share/lua/5.1/?/init.lua
    LUA_CPATH: ;;/home/runner/.luarocks/lib/lua/5.1/?.so;/home/runner/work/lua-casbin/lua-casbin/.luarocks/lib/lua/5.1/?.so
Warning: Failed searching manifest: Failed loading manifest for [https://luarocks.org:](https://luarocks.org/) Error loading file: [string "/home/runner/.cache/luarocks/https___luarocks..."]:227122: main function has more than 65536 constants
Warning: Failed searching manifest: Failed loading manifest for https://raw.githubusercontent.com/rocks-moonscript-org/moonrocks-mirror/master/: Error loading file: [string "/home/runner/.cache/luarocks/https___raw.gith..."]:225673: main function has more than 65536 constants
Warning: Failed searching manifest: Failed downloading http://luafr.org/moonrocks - Failed downloading http://luafr.org/moonrocks/manifest-5.1 - /home/runner/.cache/luarocks/http___luafr.org_moonrocks/manifest-5.1
Warning: Failed searching manifest: Failed downloading http://luarocks.logiceditor.com/rocks - Failed downloading http://luarocks.logiceditor.com/rocks/manifest-5.1 - /home/runner/.cache/luarocks/http___luarocks.logiceditor.com_rocks/manifest-5.1

Error: No results matching query were found for Lua 5.1.
To check if it is available for other Lua versions, use --check-lua-versions.
Error: Process completed with exit code 1.

[Copilot]

@copilot fix: https://github.com/casbin/lua-casbin/actions/runs/21696318490/job/62569433929?pr=169

...

Fixed in 6550a94. The benchmark job was missing the retry logic that the test job has for handling transient luarocks manifest loading failures. Added until...do...done loops around all luarocks install commands in the benchmark job to match the test job's resilient approach.