Now I try to find out whats the problem. After Node sass ~ bench start error I tried:
$ cd apps/frappe
$ yarn install
yarn install v1.22.10
warning ../../package.json: No license field
[1/4] Resolving packages...
[2/4] Fetching packages...
[3/4] Linking dependencies...
warning " > [email protected]" has unmet peer dependency "[email protected] - 3".
warning " > [email protected]" has unmet peer dependency "popper.js@^1.16.0".
warning Workspaces can only be enabled in private projects.
[4/4] Building fresh packages...
[1/4] ⠠ node-sass
[-/4] ⠠ waiting...
[-/4] ⠠ waiting...
error /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-sass: Command failed.
Exit code: 1
Command: node scripts/build.js
Arguments:
Directory: /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-sass
Output:
Building: /usr/bin/node /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-gyp/bin/node-gyp.js rebuild --verbose --libsass_ext= --libsass_cflags= --libsass_ldflags= --libsass_library=
gyp info it worked if it ends with ok
gyp verb cli [
gyp verb cli '/usr/bin/node',
gyp verb cli '/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-gyp/bin/node-gyp.js',
gyp verb cli 'rebuild',
gyp verb cli '--verbose',
gyp verb cli '--libsass_ext=',
gyp verb cli '--libsass_cflags=',
gyp verb cli '--libsass_ldflags=',
gyp verb cli '--libsass_library='
gyp verb cli ]
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp verb command rebuild []
gyp verb command clean []
gyp verb clean removing "build" directory
gyp verb command configure []
gyp verb check python checking for Python executable "python2" in the PATH
gyp verb `which` failed Error: not found: python2
gyp verb `which` failed at getNotFoundError (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:13:12)
gyp verb `which` failed at F (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:68:19)
gyp verb `which` failed at E (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:80:29)
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:89:16
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/isexe/index.js:42:5
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/isexe/mode.js:8:5
gyp verb `which` failed at FSReqCallback.oncomplete (node:fs:195:21)
gyp verb `which` failed python2 Error: not found: python2
gyp verb `which` failed at getNotFoundError (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:13:12)
gyp verb `which` failed at F (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:68:19)
gyp verb `which` failed at E (/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:80:29)
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/which/which.js:89:16
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/isexe/index.js:42:5
gyp verb `which` failed at /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/isexe/mode.js:8:5
gyp verb `which` failed at FSReqCallback.oncomplete (node:fs:195:21) {
gyp verb `which` failed code: 'ENOENT'
gyp verb `which` failed }
gyp verb check python checking for Python executable "python" in the PATH
gyp verb `which` succeeded python /disk/service/web/home/erp/bin/python
gyp ERR! configure error
gyp ERR! stack Error: Command failed: /disk/service/web/home/erp/bin/python -c import sys; print "%s.%s.%s" % sys.version_info[:3];
gyp ERR! stack File "<string>", line 1
gyp ERR! stack import sys; print "%s.%s.%s" % sys.version_info[:3];
gyp ERR! stack ^
gyp ERR! stack SyntaxError: invalid syntax
gyp ERR! stack
gyp ERR! stack at ChildProcess.exithandler (node:child_process:397:12)
gyp ERR! stack at ChildProcess.emit (node:events:394:28)
gyp ERR! stack at maybeClose (node:internal/child_process:1067:16)
gyp ERR! stack at Process.ChildProcess._handle.onexit (node:internal/child_process:301:5)
gyp ERR! System Linux 5.12.15-arch1-1
gyp ERR! command "/usr/bin/node" "/disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-gyp/bin/node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library="
gyp ERR! cwd /disk/service/web/home/erp/frappe-bench/apps/frappe/node_modules/node-sass
gyp ERR! node -v v16.5.0
gyp ERR! node-gyp -v v3.8.0
It has the same error. The error message is not really revealing if you dont have written the code yourself.
I dont understand whats the problem. All these files are available:
/usr/bin/node
apps/frappe/node_modules/node-sass
apps/frappe/node_modules/node-gyp/bin/node-gyp.js
apps/frappe/node_modules/node-sass/scripts/build.js
Is it really necessary to install python2 ??? 
Or is it version of node and node-gyp a problem:
gyp ERR! node -v v16.5.0
gyp ERR! node-gyp -v v3.8.0