Handling empty strings passed as pip_install_command.

plugins/provisioners/ansible/cap/guest/pip/pip.rb

@@ -5,6 +5,8 @@ module VagrantPlugins
       module Guest
         module Pip
 
+          DEFAULT_PIP_INSTALL_CMD = "curl https://bootstrap.pypa.io/get-pip.py | sudo python"
+
           def self.pip_install(machine, package = "", version = "", pip_args = "", upgrade = true)
             upgrade_arg = "--upgrade" if upgrade
             version_arg = ""
@@ -18,7 +20,17 @@ module VagrantPlugins
             machine.communicate.sudo "pip install #{args_array.join(' ')}"
           end
 
-          def self.get_pip(machine, pip_install_cmd="curl https://bootstrap.pypa.io/get-pip.py | sudo python")
+          def self.get_pip(machine, pip_install_cmd=DEFAULT_PIP_INSTALL_CMD)
+
+            # The objective here is to get pip either by default
+            # or by the argument passed in. The objective is not 
+            # to circumvent the pip setup by passing in nothing.
+            # Thus, we stick with the default on an empty string.
+
+            if pip_install_cmd.empty?
+              pip_install_cmd=DEFAULT_PIP_INSTALL_CMD
+            end
+
             machine.ui.detail I18n.t("vagrant.provisioners.ansible.installing_pip")
             machine.communicate.execute pip_install_cmd
           end

test/unit/plugins/provisioners/ansible/cap/guest/pip/pip_test.rb

@@ -36,6 +36,12 @@ describe VagrantPlugins::Ansible::Cap::Guest::Pip do
             expect(communicator).to receive(:execute).with(pip_install_command)
             subject.get_pip(machine,pip_install_command)
         end
+
+        it "installs pip using the default command if the argument is empty" do
+            pip_install_command = ""
+            expect(communicator).to receive(:execute).with("curl https://bootstrap.pypa.io/get-pip.py | sudo python")
+            subject.get_pip(machine,pip_install_command)
+        end        
     end    
   end
 end