`azdev test` gets error with master branch

```
❯ azdev test test_storage_blob_upload --discover

=============
| Run Tests |
=============

=====================
| Discovering Tests |
=====================

(six 1.14.0 (e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages), Requirement.parse('six==1.12'), {'astroid'})
Traceback (most recent call last):
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 573, in _build_master
ws.require(__requires__)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 891, in require
needed = self.resolve(parse_requirements(requirements))
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 782, in resolve
raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (six 1.14.0 (e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages), Requirement.parse('six==1.12'), {'astroid'})

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\knack\cli.py", line 215, in invoke
cmd_result = self.invocation.execute(args)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\knack\invocation.py", line 225, in execute
cmd_result = parsed_args.func(params)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\knack\commands.py", line 148, in __call__
return self.handler(*args, **kwargs)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\knack\commands.py", line 255, in _command_handler
result = op(client, **command_args) if client else op(**command_args)
File "e:\microsoft\azurecli\azure-cli-dev-tools\azdev\operations\testtool\__init__.py", line 48, in run_tests
test_index = _get_test_index(profile or current_profile(), discover)
File "e:\microsoft\azurecli\azure-cli-dev-tools\azdev\operations\testtool\__init__.py", line 320, in _get_test_index
test_index = _discover_tests(profile)
File "e:\microsoft\azurecli\azure-cli-dev-tools\azdev\operations\testtool\__init__.py", line 240, in _discover_tests
tests = _discover_module_tests(mod_name, mod_data)
File "e:\microsoft\azurecli\azure-cli-dev-tools\azdev\operations\testtool\__init__.py", line 174, in _discover_module_tests
module = import_module(test_file_path)
File "C:\Users\zuh\AppData\Local\Programs\Python\Python37\lib\importlib\__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1006, in _gcd_import
File "", line 983, in _find_and_load
File "", line 967, in _find_and_load_unlocked
File "", line 677, in _load_unlocked
File "", line 728, in exec_module
File "", line 219, in _call_with_frames_removed
File "e:\microsoft\azurecli\azure-cli\src\azure-cli\azure\cli\command_modules\appservice\tests\latest\test_devops_build_commands_thru_mock.py", line 10, in
from azure.cli.command_modules.appservice.azure_devops_build_interactive import (
File "e:\microsoft\azurecli\azure-cli\src\azure-cli\azure\cli\command_modules\appservice\azure_devops_build_interactive.py", line 31, in
from .azure_devops_build_provider import AzureDevopsBuildProvider
File "e:\microsoft\azurecli\azure-cli\src\azure-cli\azure\cli\command_modules\appservice\azure_devops_build_provider.py", line 7, in
from azure_functions_devops_build.project.project_manager import ProjectManager
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\azure_functions_devops_build\project\project_manager.py", line 11, in
from vsts.exceptions import VstsServiceError
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\vsts\__init__.py", line 5, in
import pkg_resources
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 3098, in
@_call_aside
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 3082, in _call_aside
f(*args, **kwargs)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 3111, in _initialize_master_working_set
working_set = WorkingSet._build_master()
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 575, in _build_master
return cls._build_from_requirements(__requires__)
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 588, in _build_from_requirements
dists = ws.resolve(reqs, Environment())
File "e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages\pkg_resources\__init__.py", line 782, in resolve
raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (six 1.14.0 (e:\microsoft\azurecli\azure-cli-extensions\env\lib\site-packages), Requirement.parse('six==1.12'), {'astroid'})
```