$ xpra start ssh:home:1 --dpi 120
2018-05-26 14:06:55,858 Xpra gtk2 client version 2.0.2-r15657 64-bit
2018-05-26 14:06:55,859  running on Linux
2018-05-26 14:06:55,862 Warning: failed to import opencv:
2018-05-26 14:06:55,863  No module named cv2
2018-05-26 14:06:55,863  webcam forwarding is disabled
2018-05-26 14:06:56,014 GStreamer version 1.10.4 for Python 2.7.14 64-bit
2018-05-26 14:06:56,099 OpenGL support is missing:
2018-05-26 14:06:56,100  cannot import name gdkgl
2018-05-26 14:06:56,131  keyboard settings: rules=evdev, model=pc104, layout=us
2018-05-26 14:06:56,132  desktop size is 2560x1440 with 1 screen:
2018-05-26 14:06:56,132   :0.0 (677x381 mm - DPI: 96x96)
2018-05-26 14:06:56,132     monitor 1 (310x170 mm - DPI: 209x215)
  File "/nix/store/2m8mhgzbh83rs9fzllzqrbdvb61pdyjh-xpra-2.2.6/bin/.xpra-wrapped", line 2
    export PATH='/nix/store/l9j2jsc9flrbmpf799nw9wdq59gpwms8-python-2.7.14/bin:/nix/store/2m8mhgzbh83rs9fzllzqrbdvb61pdyjh-xpra-2.2.6/bin:/nix/store/4d57d7z2y38k62ibb20iha8d99bqbibw-python2.7-setuptools-39.0.1/bin:/nix/store/npfphg9c3hz1qvl5fsh0xn71831v9bxd-python2.7-pygtk-2.24.0/bin:/nix/store/dx5nyyg89fdqaaix6g8r2gsywlidch3b-gtk+-2.24.32-dev/bin:/nix/store/szcis3117qd65i22322fjsk3bzljc6bc-glib-2.56.0-dev/bin:/nix/store/biv22ang6z5yviggwb0v2yydvsf82mgc-gettext-0.19.8/bin:/nix/store/80mdbn1vxj000ld7xmxcfs7r5pcwb458-cairo-1.14.10-dev/bin:/nix/store/11mvvhykc4svx4f5p5ssw5l87h7v99q6-freetype-2.9-dev/bin:/nix/store/9bf6jxxj81bncbakjr3hc27gj4q5smxl-bzip2-1.0.6.0.1-bin/bin:/nix/store/v9cz97wzqaw1rfwwj4a9fm7mmx9g3kx7-libpng-apng-1.6.34-dev/bin:/nix/store/lf0z0xq8ckvgh5nrhgmqgpnnpmk728jw-fontconfig-2.12.6-bin/bin:/nix/store/dpydsfzmxm2dfmsr1c2llvrra9y663qx-expat-2.2.5-dev/bin:/nix/store/2ck6fr449hby8haj89wnjh6zs5y2k7a6-harfbuzz-1.7.6-dev/bin:/nix/store/xwdjw18l62h2dvq814hrrvdv6g2na0y6-graphite2-1.3.6/bin:/nix/store/r2ps69k2ihvpjyajfciqk6x3n4wb93qw-pango-1.40.14-bin/bin:/nix/store/izq6b5xrn5hggnijqmlhlzsngk1yhck7-gdk-pixbuf-2.36.7-dev/bin:/nix/store/5s5q2fs2qr4l0f39ana4qcnlnq0cn5gd-libjpeg-turbo-1.5.3-bin/bin:/nix/store/f6khwaaz3lzl56x6njw9h88gfw9ns32v-xz-5.2.3-bin/bin:/nix/store/g73cpc8zn5hmmz5ks04qxzj1xrqxy0yf-libtiff-4.0.9-bin/bin:/nix/store/nari13aay7dp4ixl4hc50xs8l8fznxf1-jasper-2.0.14-bin/bin:/nix/store/fs32hdcj3rqnkyv60q3zj4dxg67wwa39-gdk-pixbuf-2.36.7/bin:/nix/store/q1lk7rmrrfq29dfx7mhbydc7lg3dx21s-cups-2.2.6-dev/bin:/nix/store/cvl545hn3r7cv2307pw7rfkj5pnhs9jc-cups-2.2.6/bin:/nix/store/9a2yw2gmhz1bvf9kf9wgjnz1k4f4p9fq-gtk+-2.24.32/bin:/nix/store/bckqrnl58pyz34ifs2zpdvsmpvq90zk3-python2.7-pygobject-2.28.6/bin:/nix/store/2lqxhdqdjf1n8vffxwcxzmsbv0kzzqr1-python2.7-numpy-1.14.2/bin:/nix/store/rhgy265vk599zvkx0wnkfz82p168fwj6-python2.7-websockify-0.7.0/bin:/nix/store/d238ml3my8zw0d98ms59qhayv80ynl1l-gstreamer-1.14.0-dev/bin:/nix/store/xwjfwxm8s5c4k7zjzdl9br0aq9kzhwnq-gst-plugins-base-1.14.0/bin:/nix/store/jh75rrglhvdjpm793zkc8jkzcpwwhajm-linux-pam-1.3.0/bin'${PATH:+':'}$PATH
              ^
SyntaxError: invalid syntax
  File "/nix/store/2m8mhgzbh83rs9fzllzqrbdvb61pdyjh-xpra-2.2.6/bin/.xpra-wrapped", line 2
    export PATH='/nix/store/l9j2jsc9flrbmpf799nw9wdq59gpwms8-python-2.7.14/bin:/nix/store/2m8mhgzbh83rs9fzllzqrbdvb61pdyjh-xpra-2.2.6/bin:/nix/store/4d57d7z2y38k62ibb20iha8d99bqbibw-python2.7-setuptools-39.0.1/bin:/nix/store/npfphg9c3hz1qvl5fsh0xn71831v9bxd-python2.7-pygtk-2.24.0/bin:/nix/store/dx5nyyg89fdqaaix6g8r2gsywlidch3b-gtk+-2.24.32-dev/bin:/nix/store/szcis3117qd65i22322fjsk3bzljc6bc-glib-2.56.0-dev/bin:/nix/store/biv22ang6z5yviggwb0v2yydvsf82mgc-gettext-0.19.8/bin:/nix/store/80mdbn1vxj000ld7xmxcfs7r5pcwb458-cairo-1.14.10-dev/bin:/nix/store/11mvvhykc4svx4f5p5ssw5l87h7v99q6-freetype-2.9-dev/bin:/nix/store/9bf6jxxj81bncbakjr3hc27gj4q5smxl-bzip2-1.0.6.0.1-bin/bin:/nix/store/v9cz97wzqaw1rfwwj4a9fm7mmx9g3kx7-libpng-apng-1.6.34-dev/bin:/nix/store/lf0z0xq8ckvgh5nrhgmqgpnnpmk728jw-fontconfig-2.12.6-bin/bin:/nix/store/dpydsfzmxm2dfmsr1c2llvrra9y663qx-expat-2.2.5-dev/bin:/nix/store/2ck6fr449hby8haj89wnjh6zs5y2k7a6-harfbuzz-1.7.6-dev/bin:/nix/store/xwdjw18l62h2dvq814hrrvdv6g2na0y6-graphite2-1.3.6/bin:/nix/store/r2ps69k2ihvpjyajfciqk6x3n4wb93qw-pango-1.40.14-bin/bin:/nix/store/izq6b5xrn5hggnijqmlhlzsngk1yhck7-gdk-pixbuf-2.36.7-dev/bin:/nix/store/5s5q2fs2qr4l0f39ana4qcnlnq0cn5gd-libjpeg-turbo-1.5.3-bin/bin:/nix/store/f6khwaaz3lzl56x6njw9h88gfw9ns32v-xz-5.2.3-bin/bin:/nix/store/g73cpc8zn5hmmz5ks04qxzj1xrqxy0yf-libtiff-4.0.9-bin/bin:/nix/store/nari13aay7dp4ixl4hc50xs8l8fznxf1-jasper-2.0.14-bin/bin:/nix/store/fs32hdcj3rqnkyv60q3zj4dxg67wwa39-gdk-pixbuf-2.36.7/bin:/nix/store/q1lk7rmrrfq29dfx7mhbydc7lg3dx21s-cups-2.2.6-dev/bin:/nix/store/cvl545hn3r7cv2307pw7rfkj5pnhs9jc-cups-2.2.6/bin:/nix/store/9a2yw2gmhz1bvf9kf9wgjnz1k4f4p9fq-gtk+-2.24.32/bin:/nix/store/bckqrnl58pyz34ifs2zpdvsmpvq90zk3-python2.7-pygobject-2.28.6/bin:/nix/store/2lqxhdqdjf1n8vffxwcxzmsbv0kzzqr1-python2.7-numpy-1.14.2/bin:/nix/store/rhgy265vk599zvkx0wnkfz82p168fwj6-python2.7-websockify-0.7.0/bin:/nix/store/d238ml3my8zw0d98ms59qhayv80ynl1l-gstreamer-1.14.0-dev/bin:/nix/store/xwjfwxm8s5c4k7zjzdl9br0aq9kzhwnq-gst-plugins-base-1.14.0/bin:/nix/store/jh75rrglhvdjpm793zkc8jkzcpwwhajm-linux-pam-1.3.0/bin'${PATH:+':'}$PATH
              ^
SyntaxError: invalid syntax
Warning: cannot use the system proxy for 'start' subcommand,
 failed to connect to '/run/xpra/system':
 [Errno 2] No such file or directory
WARNING: low display number: 1
 You are attempting to run the xpra server against a low X11 display number: ':1'.
 This is generally not what you want.
 You should probably use a higher display number just to avoid any confusion (and also this warning message).
Entering daemon mode; any further errors will be reported to:
  /run/user/1000/xpra/:1.log
xpra initialization error:
 failed to identify the new server display!
sh: /usr/local/bin/xpra: No such file or directory
2018-05-26 14:07:13,533 Error: failed to receive anything, not an xpra server?
2018-05-26 14:07:13,534   could also be the wrong protocol, username, password or port
2018-05-26 14:07:13,535 Connection lost

 - system: `"x86_64-linux"`
 - host os: `Linux 4.14.36, NixOS, 18.09.git.0f3459f (Jellyfish)`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.0.1`
 - channels(root): `"nixos, nixpkgs"`
 - channels(ben): `"nixpkgs"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs`