Fix for pip freeze with pip v20.1+

Author: smlindauer

src/sasctl/utils/misc.py

@@ -18,11 +18,20 @@ def installed_packages():
 
     Notes
     -----
-    Uses pip freeze functionality so pip module must be present.
+    Uses pip freeze functionality so pip module must be present. For pip 
+    versions >=20.1, this functionality fails to provide versions for some
+    conda installed, locally installed, and url installed packages. Instead
+    uses the pkg_resources package which is typically bundled with pip.
 
     """
+    from packaging import version
     try:
-        from pip._internal.operations import freeze
+        import pip
+        if version.parse(pip.__version__) >= version.parse("20.1"):
+            import pkg_resources
+            return [p.project_name + "==" + p.version for p in pkg_resources.working_set]
+        else:
+            from pip._internal.operations import freeze
     except ImportError:
         try:
             from pip.operations import freeze