refactor: lazy imports of expensive libs

Author: DanielMicrosoft

.vscode/launch.json

@@ -3,42 +3,34 @@
     "configurations": [
         {
             "name": "Azure CLI Debug (Integrated Console)",
-            "type": "python",
+            "type": "debugpy",
             "request": "launch",
             "python": "${command:python.interpreterPath}",
             "program": "${workspaceRoot}/src/azure-cli/azure/cli/__main__.py",
             "cwd": "${workspaceRoot}",
             "args": [
-                "--help"
+                "Version"
             ],
             "console": "integratedTerminal",
-            "debugOptions": [
-                "WaitOnAbnormalExit",
-                "WaitOnNormalExit",
-                "RedirectOutput"
-            ],
             "justMyCode": false
         },
         {
             "name": "Azure CLI Debug (External Console)",
-            "type": "python",
+            "type": "debugpy",
             "request": "launch",
             "stopOnEntry": true,
             "python": "${command:python.interpreterPath}",
             "program": "${workspaceRoot}/src/azure-cli/azure/cli/__main__.py",
             "cwd": "${workspaceRoot}",
             "args": [
-                "--help"
+                "VERSION"
             ],
             "console": "externalTerminal",
-            "debugOptions": [
-                "WaitOnAbnormalExit",
-                "WaitOnNormalExit"
-            ]
+            "justMyCode": false
         },
         {
             "name": "Azdev Scripts",
-            "type": "python",
+            "type": "debugpy",
             "request": "launch",
             "python": "${command:python.interpreterPath}",
             "program": "${workspaceRoot}/tools/automation/__main__.py",
@@ -47,11 +39,6 @@
                 "--help"
             ],
             "console": "integratedTerminal",
-            "debugOptions": [
-                "WaitOnAbnormalExit",
-                "WaitOnNormalExit",
-                "RedirectOutput"
-            ]
         }
     ]
-}
+}

src/azure-cli-core/azure/cli/core/util.py

@@ -8,14 +8,12 @@
 import binascii
 import getpass
 import json
-import yaml
 import logging
 import os
 import platform
 import re
 import ssl
 import sys
-from urllib.request import urlopen
 
 from knack.log import get_logger
 from knack.util import CLIError, to_snake_case, to_camel_case
@@ -534,6 +532,7 @@ def get_file_json(file_path, throw_on_empty=True, preserve_order=False):
 
 
 def get_file_yaml(file_path, throw_on_empty=True):
+    import yaml
     content = read_file_content(file_path)
     if not content:
         if throw_on_empty:
@@ -1168,6 +1167,7 @@ def _ssl_context():
 
 
 def urlretrieve(url):
+    from urllib.request import urlopen
     req = urlopen(url, context=_ssl_context())
     return req.read()