Add env and env var values

src/pip/_internal/commands/configuration.py

@@ -195,6 +195,7 @@ def unset_name(self, options, args):
 
     def list_config_values(self, options, args):
         self._get_n_args(args, "debug", n=0)
+        self.print_env_var_values()
         for variant, files in sorted(self.configuration.iter_config_files()):
             write_output("%s:", variant)
             for fname in files:
@@ -211,6 +212,13 @@ def print_config_file_values(self, variant):
             with indent_log():
                 write_output("%s: %s ", name, value)
 
+    def print_env_var_values(self):
+        write_output("%s:", 'env_var')
+        with indent_log():
+            for key, value in self.configuration.get_environ_vars():
+                env_var = 'PIP_{}'.format(key.upper())
+                write_output("%s=%r", env_var, value)
+
     def open_in_editor(self, options, args):
         editor = self._determine_editor(options)
 

src/pip/_internal/configuration.py

@@ -342,7 +342,7 @@ def _load_environment_vars(self):
         """Loads configuration from environment variables
         """
         self._config[kinds.ENV_VAR].update(
-            self._normalized_keys(":env:", self._get_environ_vars())
+            self._normalized_keys(":env:", self.get_environ_vars())
         )
 
     def _normalized_keys(self, section, items):
@@ -358,7 +358,7 @@ def _normalized_keys(self, section, items):
             normalized[key] = val
         return normalized
 
-    def _get_environ_vars(self):
+    def get_environ_vars(self):
         # type: () -> Iterable[Tuple[str, str]]
         """Returns a generator with all environmental vars with prefix PIP_"""
         for key, val in os.environ.items():