I am getting these errors and the svg is not flipped on Fedora 33 x86-64:

```
shlomif[homepage]:$trunk$ ./gen-helpers

(org.inkscape.Inkscape:54183): Gtk-WARNING **: 17:39:13.001: Theme parsing error: gtk.css:2:33: Failed to import: Error opening file /home/shlomif/.config/gtk-3.0/window_decorations.css: No such file or directory
+ inkscape --actions 'EditSelectAll;ObjectFlipHorizontally' --export-filename src/images/evilphish-svg--facing-right.svg src/images/evilphish-svg--facing-left.svg

(org.inkscape.Inkscape:54197): Gtk-WARNING **: 17:39:13.096: Theme parsing error: gtk.css:2:33: Failed to import: Error opening file /home/shlomif/.config/gtk-3.0/window_decorations.css: No such file or directory
WARNING: ignoring verb EditSelectAll - GUI required for this verb.

** (org.inkscape.Inkscape:54197): CRITICAL **: 17:39:13.288: static void Inkscape::EditVerb::perform(SPAction*, void*): assertion 'ensure_desktop_valid(action)' failed
WARNING: ignoring verb ObjectFlipHorizontally - GUI required for this verb.

** (org.inkscape.Inkscape:54197): CRITICAL **: 17:39:13.288: static void Inkscape::ObjectVerb::perform(SPAction*, void*): assertion 'ensure_desktop_valid(action)' failed
shlomif[homepage]:$trunk$ inkscape --version

(org.inkscape.Inkscape:54343): Gtk-WARNING **: 17:41:28.451: Theme parsing error: gtk.css:2:33: Failed to import: Error opening file /home/shlomif/.config/gtk-3.0/window_decorations.css: No such file or directory
Inkscape 1.0.1 (3bc2e813f5, 2020-09-07)
    Pango version: 1.48.0
shlomif[homepage]:$trunk$ which inkscape
/usr/bin/inkscape
shlomif[homepage]:$trunk$
```