Add --no-index to ensure pip install is offline

Author: ChuckQuinnIV

pip_install_process.go

@@ -32,7 +32,7 @@ func (p PipInstallProcess) Execute(srcPath, targetLayerPath string) error {
 
 	err := p.executable.Execute(pexec.Execution{
 		// Install pip from source with the pip that comes pre-installed with cpython
-		Args: []string{"-m", "pip", "install", srcPath, "--user", fmt.Sprintf("--find-links=%s", srcPath)},
+		Args: []string{"-m", "pip", "install", srcPath, "--user", "--no-index", fmt.Sprintf("--find-links=%s", srcPath)},
 		// Set the PYTHONUSERBASE to ensure that pip is installed to the newly created target layer.
 		Env:    append(os.Environ(), fmt.Sprintf("PYTHONUSERBASE=%s", targetLayerPath)),
 		Stdout: buffer,

pip_install_process_test.go

@@ -45,7 +45,7 @@ func testPipInstallProcess(t *testing.T, context spec.G, it spec.S) {
 				Expect(err).NotTo(HaveOccurred())
 
 				Expect(executable.ExecuteCall.Receives.Execution.Env).To(Equal(append(os.Environ(), fmt.Sprintf("PYTHONUSERBASE=%s", targetLayerPath))))
-				Expect(executable.ExecuteCall.Receives.Execution.Args).To(Equal([]string{"-m", "pip", "install", srcLayerPath, "--user", fmt.Sprintf("--find-links=%s", srcLayerPath)}))
+				Expect(executable.ExecuteCall.Receives.Execution.Args).To(Equal([]string{"-m", "pip", "install", srcLayerPath, "--user", "--no-index", fmt.Sprintf("--find-links=%s", srcLayerPath)}))
 			})
 		})