fix for ubuntu 20.04 (#748)

requirements.txt

@@ -12,3 +12,4 @@ pygments
 capstone==4.0.1
 enum34
 pytest
+testresources

setup.sh

@@ -20,7 +20,9 @@ osx() {
 
 install_apt() {
     sudo apt-get update || true
-    sudo apt-get -y install gdb python-dev python3-dev python-pip python3-pip libglib2.0-dev libc6-dbg
+    # This breaks Ubuntu 20.04, but is probably still needed for older version
+    sudo apt-get -y  python-pip || true
+    sudo apt-get -y install gdb python-dev python3-dev python3-pip libglib2.0-dev libc6-dbg
 
     if uname -m | grep x86_64 > /dev/null; then
         sudo apt-get -y install libc6-dbg:i386 || true