Use --no-use-pep517 flag for editable mode with pyproject.toml (#455)

* Use --no-use-pep517 flag for editable mode during installation and update docs to reflect this
   - pypa/pip#6434
   - pypa/pip#6442
* Add .eggs to Black exclude list

.travis.yml

@@ -10,7 +10,7 @@ before_install:
   - export LD_PRELOAD="/usr/lib/libtcmalloc_minimal.so.4"
   - pip install --upgrade pip setuptools wheel
 install:
-  - pip install --ignore-installed -U -q -e .[complete]
+  - pip install --ignore-installed -U -q --no-use-pep517 -e .[complete]
   - pip freeze
 script:
   - pyflakes pyhf
@@ -69,7 +69,7 @@ jobs:
       - export LD_PRELOAD="/usr/lib/libtcmalloc_minimal.so.4"
       - pip install --upgrade pip setuptools wheel
     install:
-      - pip install --ignore-installed -U -q -e .[complete]
+      - pip install --ignore-installed -U -q --no-use-pep517 -e .[complete]
       - pip freeze
     script: python -m pytest -r sx --benchmark-sort=mean tests/benchmarks/
     after_success: skip
@@ -82,7 +82,7 @@ jobs:
       - export LD_PRELOAD="/usr/lib/libtcmalloc_minimal.so.4"
       - pip install --upgrade pip setuptools wheel
     install:
-      - pip install --ignore-installed -U -q -e .[complete]
+      - pip install --ignore-installed -U -q --no-use-pep517 -e .[complete]
       - pip freeze
     script:
       - python -m doctest README.md

docs/development.rst

@@ -11,7 +11,7 @@ and install all necessary packages for development
 
 .. code-block:: console
 
-    pip install --ignore-installed -U -e .[complete]
+    pip install --ignore-installed -U --no-use-pep517 -e .[complete]
 
 Then setup the Git pre-commit hook for `Black <https://github.com/ambv/black>`__  by running
 

pyproject.toml

@@ -7,6 +7,7 @@ include = '\.pyi?$'
 exclude = '''
 /(
     \.git
+  | .eggs
   | build
 )/
 '''