Update dh-virtualenv so it supports specifying custom pip binary to copy

to and use inside the created dh virtual environment.

In addition to that, update create_virtualenv() step to print actual
versions of the tools which are installed into virtualenv.

This new --pip-binary flag should be used in combination with
--virtualenv-extra-args="--no-pip" where we want to use a correct system
version of pip is used instead of the one bundled with virtual
environment.

Also add --force-pip-version which allows us to install a specific
version of pip inside venv.

dh_virtualenv/cmdline.py

@@ -98,6 +98,13 @@ def get_default_parser():
                       "you'll install this program by using the --preinstall "
                       "argument. The replacement is expected to be found in "
                       "the virtualenv's bin/ directory.")
+    parser.add_option('--pip-binary', default=None,
+                      help="Path to custom pip binary which should be used "
+                           "and  copied to dh virtualenv. Should be used in "
+                           "combination with virtualenv --no-pip flag")
+    parser.add_option('--force-pip-version', default=None,
+                      help="Force upgrade a specific pip version in dh "
+                           "dh-virtualenv")
     parser.add_option('--upgrade-pip', action='store_true', default=False,
                       help='Upgrade pip to the latest available version')
     parser.add_option('--extra-pip-arg', action='append',

dh_virtualenv/deployment.py

@@ -35,6 +35,8 @@ def __init__(self,
                  extra_urls=[],
                  preinstall=[],
                  pip_tool='pip',
+                 pip_binary=None,
+                 force_pip_version=None,
                  upgrade_pip=False,
                  index_url=None,
                  setuptools=False,
@@ -66,6 +68,9 @@ def __init__(self,
         self.bin_dir = os.path.join(self.package_dir, 'bin')
         self.local_bin_dir = os.path.join(self.package_dir, 'local', 'bin')
 
+        self.pip_binary = pip_binary
+        self.force_pip_version = force_pip_version
+
         self.preinstall = preinstall
         self.upgrade_pip = upgrade_pip
         self.extra_virtualenv_arg = extra_virtualenv_arg
@@ -108,6 +113,8 @@ def from_options(cls, package, options):
                    extra_urls=options.extra_index_url,
                    preinstall=options.preinstall,
                    pip_tool=options.pip_tool,
+                   pip_binary=options.pip_binary,
+                   force_pip_version=options.force_pip_version,
                    upgrade_pip=options.upgrade_pip,
                    index_url=options.index_url,
                    setuptools=options.setuptools,
@@ -152,6 +159,38 @@ def create_virtualenv(self):
         virtualenv.append(self.package_dir)
         subprocess.check_call(virtualenv)
 
+        if self.force_pip_version:
+            venv_pip_path = self.venv_bin('pip')
+            print("Forcing / upgrading pip version inside venv to %s..." % (self.force_pip_version))
+            output = subprocess.check_output([venv_pip_path, 'install', '--upgrade',
+                                              'pip==%s' % (self.force_pip_version)]).strip()
+            print('Output: %s' % (output))
+
+        if self.pip_binary:
+            dest_path = self.venv_bin('pip')
+            print("Copying %s pip binary into dh virtualenv: %s..." % (self.pip_binary, dest_path))
+            shutil.copy(self.pip_binary, dest_path)
+
+        # To make troubleshooting, etc. easier, we also print which versions
+        # were copied and used into venv
+        venv_python_path = self.venv_bin('python')
+        venv_virtualenv_path = self.venv_bin('virtualenv')
+        venv_pip_path = self.venv_bin('pip')
+
+        print('dh-virualenv versions info')
+
+        if os.path.exists(venv_python_path):
+            output = subprocess.check_output([venv_python_path, '--version']).strip()
+            print('Using Python: %s' % (output))
+
+        if os.path.exists(venv_virtualenv_path):
+            output = subprocess.check_output([venv_virtualenv_path, '--version']).strip()
+            print('Using virtualenv: %s' % (output))
+
+        if os.path.exists(venv_pip_path):
+            output = subprocess.check_output([venv_pip_path, '--version']).strip()
+            print('Using pip: %s' % (output))
+
     def venv_bin(self, binary_name):
         return os.path.abspath(os.path.join(self.bin_dir, binary_name))