python pip use --target instead of --root

Author: NicholasBHubbard

.github/workflows/ruby.yml

@@ -22,11 +22,6 @@ jobs:
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Run test suite
       run: |
-        # use a Python venv to avoid the mess of interacting with system Python packages
-        python -m venv venv
-        . venv/bin/activate
-        pip install -r requirements.txt -r spec/test-requirements.txt
-
         if [ ! -z "$RUNNER_DEBUG" ] ; then
           DEBUG=1 bundle exec rspec -fd
         else

lib/fpm/package/python.rb

@@ -594,6 +594,12 @@ def fix_name(name)
     end
   end # def fix_name
 
+  def pip_install_dir()
+    execmd([attributes[:python_bin], "-c", "import sysconfig; from pathlib import Path; print(Path(sysconfig.get_path('purelib')).parent)"], :stdin => false, :stderr => false) do |stdout|
+      return stdout.read(64<<10).strip()
+    end
+  end
+
   # Install this package to the staging directory
   def install_to_staging(path)
     prefix = "/"
@@ -602,10 +608,10 @@ def install_to_staging(path)
     # XXX: Note: pip doesn't seem to have any equivalent to `--install-lib` or similar flags.
     # XXX: Deprecate :python_install_data, :python_install_lib, :python_install_bin
     # XXX: Deprecate: :python_setup_py_arguments
-    flags = [ "--root", staging_path ]
-    flags += [ "--prefix", prefix ] if !attributes[:prefix].nil?
-
+    flags = [ "--target", staging_path + pip_install_dir() ]
+    #flags += [ "--prefix", prefix ] if !attributes[:prefix].nil?
     safesystem(*attributes[:python_pip], "install", "--no-deps", *flags, path)
+    require 'pry'; binding.pry #DEBUG:
   end # def install_to_staging
 
   public(:input)