x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/tmp/pip_build_gnuhealth/lxml/src/lxml/includes -I/usr/include/python2.7 -c src/lxml/lxml.etree.c -o build/temp.linux-x86_64-2.7/src/lxml/lxml.etree.o -w
In file included from src/lxml/lxml.etree.c:239:0:
/tmp/pip_build_gnuhealth/lxml/src/lxml/includes/etree_defs.h:14:31: fatal error: libxml/xmlversion.h: No such file or directory
#include "libxml/xmlversion.h"
^
compilation terminated.
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1