Comment 8 for bug 1662531

the crash in trunk was diagnosed further by printing the output coming from the Popen command. The following code was used to examine the output:
    f = p.communicate()
    err.close()
    inkex.errormsg(str(f))

When this code was run on 0.92.x, Inkscape 0.92.0 r15299
the result was f = ('', '') as expected

When this code was run on trunk, Inkscape 0.92+devel 15458
the result was:
f = ('', "terminate called after throwing an instance of 'std::runtime_error'\r\n what(): locale::facet::_S_create_c_locale name not valid\r\n\r\nEmergency save activated!\r\nEmergency save completed. Inkscape will close now.\r\nIf you can reproduce this crash, please file a bug at www.inkscape.org\r\nwith a detailed description of the steps leading to the crash, so we can fix it.\r\nGtk-Message: GtkDialog mapped without a transient parent. This is discouraged.\r\n")

it appears that the crash is caused by a gtk message