building Nix...
building the system configuration...
error: while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `system' at `/etc/nixos/nixos/modules/system/activation/top-level.nix:146:5':
while evaluating the derivation attribute `buildCommand' at `/etc/nixos/nixos/modules/system/activation/top-level.nix:147:5':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `etc' at `/etc/nixos/nixos/modules/system/etc/etc.nix:41:5':
while evaluating the derivation attribute `sources' at `/etc/nixos/nixos/modules/system/etc/etc.nix:46:5':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `upstart-xserver.conf' at `/etc/nixos/nixpkgs/pkgs/build-support/trivial-builders.nix:10:14':
while evaluating the derivation attribute `jobText' at `/etc/nixos/nixos/modules/system/upstart/upstart.nix:111:43':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/strings.nix:18:25':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/strings.nix:14:32':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/strings.nix:14:32':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/strings.nix:14:32':
while evaluating the builtin function `head':
while evaluating the function at `/etc/nixos/nixos/modules/system/upstart/upstart.nix:44:31':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `slim.cfg' at `/etc/nixos/nixpkgs/pkgs/build-support/trivial-builders.nix:10:14':
while evaluating the derivation attribute `text' at `/etc/nixos/nixpkgs/pkgs/build-support/trivial-builders.nix:21:29':
while evaluating the attribute `xserverArgs' at `/etc/nixos/nixpkgs/pkgs/lib/attrsets.nix:108:41':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/modules.nix:191:43':
while evaluating the attribute `result' at `/etc/nixos/nixpkgs/pkgs/lib/modules.nix:303:11':
while evaluating the builtin function `addErrorContext':

while evaluating the option `services.xserver.displayManager.xserverArgs':
The error may come from the following files:
/etc/nixos/nixos/modules/services/x11/xserver.nix
/etc/nixos/nixos/modules/services/x11/display-managers/default.nix

while evaluating the builtin function `toString':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `xserver.conf' at `/etc/nixos/nixos/modules/services/x11/xserver.nix:55:5':
while evaluating the derivation attribute `config' at `/etc/nixos/nixos/modules/services/x11/xserver.nix:60:18':
while evaluating the attribute `config' at `/etc/nixos/nixpkgs/pkgs/lib/attrsets.nix:108:41':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/modules.nix:191:43':
while evaluating the attribute `result' at `/etc/nixos/nixpkgs/pkgs/lib/modules.nix:303:11':
while evaluating the builtin function `addErrorContext':

while evaluating the option `services.xserver.config':
The error may come from the following files:
/etc/nixos/nixos/modules/services/x11/xserver.nix
/etc/nixos/nixos/modules/services/x11/hardware/wacom.nix
/etc/nixos/nixos/modules/services/x11/hardware/synaptics.nix

while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/trivial.nix:4:8':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/modules.nix:121:26':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:124:20':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:50:18':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the builtin function `addErrorContext':
while evaluating properties:
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:152:33':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/misc.nix:170:17':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:134:25':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:50:18':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:51:14':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:135:13':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:20:14':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:13:12':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:12:13':
while evaluating the builtin function `isAttrs':
while evaluating the builtin function `head':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:141:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:48:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:35:16':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:13:12':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:12:13':
while evaluating the builtin function `isAttrs':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/attrsets.nix:41:16':
while evaluating the builtin function `getAttr':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:75:16':
while evaluating the builtin function `addErrorContext':
while moving properties on the attribute `config':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:101:40':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/lists.nix:17:19':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/misc.nix:170:17':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:48:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:105:35':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:48:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:35:16':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:13:12':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:12:13':
while evaluating the builtin function `isAttrs':
while evaluating the attribute `content' at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:51:9':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:48:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:35:16':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:13:12':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/types.nix:12:13':
while evaluating the builtin function `isAttrs':
while evaluating the attribute `content' at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:51:9':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:48:27':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/properties.nix:180:22':
while evaluating the function at `/etc/nixos/nixpkgs/pkgs/lib/attrsets.nix:41:16':
while evaluating the builtin function `getAttr':
cannot coerce an attribute set (except a derivation) to a string