CI is falling over when installing python dependencies

[DonJayamanne]

Here's the error

2019-01-22T21:13:50.8166037Z [command]/opt/hostedtoolcache/Python/3.7.0/x64/python -m pip --disable-pip-version-check install -t ./pythonFiles/lib/python --no-cache-dir --implementation py --no-deps --upgrade -r requirements.txt
2019-01-22T21:13:51.6232520Z Collecting jedi==0.12.0 (from -r requirements.txt (line 1))
2019-01-22T21:13:51.6237881Z   Downloading https://files.pythonhosted.org/packages/e7/42/074192a165622e645ed4aeade63e76e56b3496a044569b3c6cae3a918352/jedi-0.12.0-py2.py3-none-any.whl (172kB)
2019-01-22T21:13:51.6238512Z Collecting parso==0.2.1 (from -r requirements.txt (line 2))
2019-01-22T21:13:51.6239372Z   Downloading https://files.pythonhosted.org/packages/cd/3e/5908f9577dbd1e5df53e64349bfd11e46b726c1e4d8cd676bbe8aa4de316/parso-0.2.1-py2.py3-none-any.whl (91kB)
2019-01-22T21:13:51.6239770Z Collecting isort==4.3.4 (from -r requirements.txt (line 3))
2019-01-22T21:13:51.6240219Z   Downloading https://files.pythonhosted.org/packages/1f/2c/22eee714d7199ae0464beda6ad5fedec8fee6a2f7ffd1e8f1840928fe318/isort-4.3.4-py3-none-any.whl (45kB)
2019-01-22T21:13:51.6240529Z Collecting ptvsd==4.2.0 (from -r requirements.txt (line 4))
2019-01-22T21:13:51.6240869Z   Downloading https://files.pythonhosted.org/packages/47/2b/4d390d097702f13dfcebc2be08996aff7ccb4a53732504144db534082140/ptvsd-4.2.0.zip (1.4MB)
2019-01-22T21:14:09.2613618Z Exception:
2019-01-22T21:14:09.2614447Z Traceback (most recent call last):
2019-01-22T21:14:09.2615618Z   File "/opt/hostedtoolcache/Python/3.7.0/x64/lib/python3.7/site-packages/pip/_internal/cli/base_command.py", line 176, in main
2019-01-22T21:14:09.2616044Z     status = self.run(options, args)
2019-01-22T21:14:09.2616918Z   File "/opt/hostedtoolcache/Python/3.7.0/x64/lib/python3.7/site-packages/pip/_internal/commands/install.py", line 346, in run
2019-01-22T21:14:09.2617270Z     session=session, autobuilding=True
2019-01-22T21:14:09.2617786Z   File "/opt/hostedtoolcache/Python/3.7.0/x64/lib/python3.7/site-packages/pip/_internal/wheel.py", line 848, in build
2019-01-22T21:14:09.2618152Z     assert building_is_possible
2019-01-22T21:14:09.2618441Z AssertionError

I get the exact same error on my Mac:

$ python -m pip --disable-pip-version-check install -t ./pythonFiles/lib/python --no-cache-dir --implementation py --no-deps --upgrade -r requirements.txt
Collecting jedi==0.12.0 (from -r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/e7/42/074192a165622e645ed4aeade63e76e56b3496a044569b3c6cae3a918352/jedi-0.12.0-py2.py3-none-any.whl (172kB)
    100% |████████████████████████████████| 174kB 11.6MB/s 
Collecting parso==0.2.1 (from -r requirements.txt (line 2))
  Downloading https://files.pythonhosted.org/packages/cd/3e/5908f9577dbd1e5df53e64349bfd11e46b726c1e4d8cd676bbe8aa4de316/parso-0.2.1-py2.py3-none-any.whl (91kB)
    100% |████████████████████████████████| 92kB 14.4MB/s 
Collecting isort==4.3.4 (from -r requirements.txt (line 3))
  Downloading https://files.pythonhosted.org/packages/1f/2c/22eee714d7199ae0464beda6ad5fedec8fee6a2f7ffd1e8f1840928fe318/isort-4.3.4-py3-none-any.whl (45kB)
    100% |████████████████████████████████| 51kB 55.1MB/s 
Collecting ptvsd==4.2.0 (from -r requirements.txt (line 4))
  Downloading https://files.pythonhosted.org/packages/47/2b/4d390d097702f13dfcebc2be08996aff7ccb4a53732504144db534082140/ptvsd-4.2.0.zip (1.4MB)
    100% |████████████████████████████████| 1.4MB 18.7MB/s 
Exception:
Traceback (most recent call last):
  File "/Users/donjayamanne/.local/share/virtualenvs/vscode-python-upstream-y9uoW8mz/lib/python3.7/site-packages/pip/_internal/cli/base_command.py", line 176, in main
    status = self.run(options, args)
  File "/Users/donjayamanne/.local/share/virtualenvs/vscode-python-upstream-y9uoW8mz/lib/python3.7/site-packages/pip/_internal/commands/install.py", line 346, in run
    session=session, autobuilding=True
  File "/Users/donjayamanne/.local/share/virtualenvs/vscode-python-upstream-y9uoW8mz/lib/python3.7/site-packages/pip/_internal/wheel.py", line 848, in build
    assert building_is_possible
AssertionError

[d3r3kk]

pip just updated to version 19.0 today.

[DonJayamanne]

Upstream issue pypa/pip#6158

[d3r3kk]

Update to pip 19 in #4089

[DonJayamanne]

Fixed.