Poetry Install with `pip` unavailable shouldn't throw Exception (#4522)

When installing Poetry through `install-poetry.py`, if `pip` is not
available, Exception should not be raised, rather installation should
be aborted with user-friendly error msg.

Fixes #4521

Co-authored-by: TurtleNishant <nishant@turtlelectric.com>
Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

install-poetry.py

@@ -516,10 +516,11 @@ class Installer:
         env_path = self._data_dir.joinpath("venv")
 
         with temporary_directory() as tmp_dir:
-            subprocess.call(
+            subprocess.run(
                 [sys.executable, "-m", "pip", "install", "virtualenv", "-t", tmp_dir],
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT,
+                check=True,
             )
 
             sys.path.insert(0, tmp_dir)