Slow updates to pip (microsoft#4087)

- v19.0 breaks our CI

Author: d3r3kk

.travis.yml

@@ -65,7 +65,7 @@ install:
  - travis_wait 5 npm ci
  - npm run clean
  - npx gulp prePublishNonBundle
- - python -m pip install --upgrade pip
+ - python -m pip install --upgrade 'pip<19'
  - python -m pip install --upgrade -r ./build/test-requirements.txt
  - npx gulp installPythonLibs
 

build/ci/templates/compile-and-validate.yml

@@ -145,7 +145,7 @@ jobs:
  inputs:
  filename: python
 
- arguments: '-m pip install --upgrade pip'
+ arguments: '-m pip install --upgrade "pip<19"'
 
 
  - task: CmdLine@1

build/ci/templates/test-phase.yml

@@ -118,7 +118,7 @@ steps:
  inputs:
  filename: python
 
- arguments: '-m pip install --upgrade pip'
+ arguments: '-m pip install --upgrade "pip<19"'
 
 
  - task: CmdLine@1