Have pip download packages to the build_path

Prior to this change, pip would download Python packages to $PWD which
leaves files hanging around.

The build_path is automatically removed when fpm exits.

lib/fpm/package/python.rb

@@ -79,7 +79,11 @@ class FPM::Package::Python < FPM::Package
   option "--setup-py-arguments", "setup_py_argument",
     "Arbitrary argument(s) to be passed to setup.py",
     :multivalued => true, :attribute_name => :python_setup_py_arguments,
-    :default => []
+    :default => [] 
+  option "--internal-pip", :flag,
+    "Use the pip module within python to install modules - aka 'python -m pip'. This is the recommended usage since Python 3.4 (2014) instead of invoking the 'pip' script",
+    :attribute_name => :python_internal_pip,
+    :default => true
 
   private
 
@@ -130,23 +134,24 @@ class FPM::Package::Python < FPM::Package
     target = build_path(package)
     FileUtils.mkdir(target) unless File.directory?(target)
 
-    if attributes[:python_pip].nil?
-      # no pip, use easy_install
-      logger.debug("no pip, defaulting to easy_install", :easy_install => attributes[:python_easyinstall])
-      safesystem(attributes[:python_easyinstall], "-i",
-                 attributes[:python_pypi], "--editable", "-U",
-                 "--build-directory", target, want_pkg)
-    else
+    if attributes[:python_internal_pip?]
+      # XXX: Should we detect if internal pip is available?
+      attributes[:python_pip] = [ attributes[:python_bin], "-m", "pip"]
+    end
+
+    # attributes[:python_pip] -- expected to be a path
+    if attributes[:python_pip]
       logger.debug("using pip", :pip => attributes[:python_pip])
       # TODO: Support older versions of pip
 
+      pip = [attributes[:python_pip]] if pip.is_a?(String)
       setup_cmd = [
-        attributes[:python_pip],
+        *attributes[:python_pip],
         "download",
         "--no-clean",
         "--no-deps",
-        "--no-binary",
-        ":all:",
+        "--no-binary", ":all:",
+        "-d", build_path,
         "-i", attributes[:python_pypi],
       ]
 
@@ -164,6 +169,12 @@ class FPM::Package::Python < FPM::Package
       ]
       
       safesystem(*setup_cmd)
+    else
+      # no pip, use easy_install
+      logger.debug("no pip, defaulting to easy_install", :easy_install => attributes[:python_easyinstall])
+      safesystem(attributes[:python_easyinstall], "-i",
+                 attributes[:python_pypi], "--editable", "-U",
+                 "--build-directory", target, want_pkg)
     end
 
     # easy_install will put stuff in @tmpdir/packagename/, so find that:

spec/fixtures/python/setup.py

@@ -10,6 +10,9 @@ setup(name="Example",
       package_dir={},
       install_requires=[
           "Dependency1", "dependency2",
+          # XXX: I don't know what these python_version-dependent deps mean
+          # needs investigation
+          # Reference: PEP-0508
            'rtxt-dep3; python_version == "2.0"',
            'rtxt-dep4; python_version > "2.0"',
            ],

spec/fpm/package/python_spec.rb

@@ -3,13 +3,19 @@ require "fpm" # local
 require "fpm/package/python" # local
 require "find" # stdlib
 
+def find_python
+  [ "python", "python3", "python2" ].each do |i|
+    return i if program_exists?(i)
+  end
+  return nil
+end
+
 def python_usable?
-  return program_exists?("python") && program_exists?("easy_install")
+  return find_python
 end
 
 if !python_usable?
-  Cabin::Channel.get("rspec").warn("Skipping Python#input tests because " \
-    "'python' and/or 'easy_install' isn't in your PATH")
+  Cabin::Channel.get("rspec").warn("Skipping Python#input tests because 'python' wasn't found in $PATH")
 end
 
 is_travis = ENV["TRAVIS_OS_NAME"] && !ENV["TRAVIS_OS_NAME"].empty?
@@ -28,7 +34,8 @@ end
 
 describe FPM::Package::Python do
   before do
-    skip("Python and/or easy_install not found") unless python_usable?
+    skip("Python program not found") unless python_usable?
+    subject.attributes[:python_bin] = find_python
   end
 
   let (:example_dir) do
@@ -124,7 +131,8 @@ describe FPM::Package::Python do
 
     it "it should include the dependencies from setup.py" do
       subject.input(example_dir)
-      insist { subject.dependencies.sort } == ["python-dependency1  ","python-dependency2  "]
+      # XXX: Why is there extra whitespace in these strings?
+      insist { subject.dependencies.sort } == ["python-dependency1  ","python-dependency2  ", "python-rtxt-dep4  "]
     end
 
     context "and :python_disable_dependency is set" do
@@ -134,7 +142,7 @@ describe FPM::Package::Python do
 
       it "it should exclude the dependency" do
         subject.input(example_dir)
-        insist { subject.dependencies.sort } == ["python-dependency2  "]
+        insist { subject.dependencies.sort } == ["python-dependency2  ", "python-rtxt-dep4  "]
       end
     end
   end