restore PEP-517 support

Co-authored-by: "Noah D. Brenowitz" <[email protected]>

.travis.yml

@@ -4,10 +4,10 @@ env:
     matrix:
         - NAME="Minimum dependencies."
           PYTHON_VERSION=3.6
-          PACKAGES="cython=0.28.5 matplotlib=2.2.2 numpy=1.16 owslib=0.17 proj4=5.2.0 scipy=1.2.0"
+          PACKAGES="matplotlib=2.2.2 numpy=1.16 owslib=0.17 proj4=5.2.0 scipy=1.2.0"
         - NAME="Latest everything."
           PYTHON_VERSION=3.8
-          PACKAGES="cython fiona matplotlib-base numpy proj pykdtree scipy"
+          PACKAGES="fiona matplotlib-base proj pykdtree scipy"
 
 
 sudo: false

INSTALL

@@ -47,7 +47,7 @@ using the `setup.py` file::
 Required dependencies
 ~~~~~~~~~~~~~~~~~~~~~
 In order to install Cartopy, or to access its basic functionality, it will be
-necessary to first install **GEOS**, **NumPy**, **Cython**, **Shapely**, and
+necessary to first install **GEOS**, **Shapely**, and
 **pyshp**. Many of these packages can be installed using pip or
 other package managers such as apt-get (Linux) and brew (macOS). Many of these
 dependencies are built as part of Cartopy's conda distribution, and the recipes
@@ -56,7 +56,7 @@ for these packages can be found at https://github.com/conda-forge/feedstocks.
 For macOS, the required dependencies can be installed in the following way::
 
     brew install proj geos
-    pip3 install --upgrade cython numpy pyshp
+    pip3 install --upgrade pyshp
     # shapely needs to be built from source to link to geos. If it is already
     # installed, uninstall it by: pip3 uninstall shapely
     pip3 install shapely --no-binary shapely
@@ -79,12 +79,6 @@ Further information about the required dependencies can be found here:
 
 **Python** 3.5 or later (https://www.python.org/)
 
-**Cython** 0.28 or later (https://pypi.python.org/pypi/Cython/)
-
-**NumPy** 1.10 or later (https://numpy.org/)
-    Python package for scientific computing including a powerful N-dimensional
-    array object.
-
 **GEOS** 3.3.3 or later (https://trac.osgeo.org/geos/)
     GEOS is an API of spatial predicates and functions for processing geometry
     written in C++.

pyproject.toml

@@ -0,0 +1,10 @@
+[build-system]
+requires = [
+    "wheel",
+    "setuptools >= 40.6.0",
+    "Cython >= 0.29.2",
+    "oldest-supported-numpy",
+    "setuptools_scm",
+    "setuptools_scm_git_archive",
+]
+build-backend = "setuptools.build_meta"

requirements/default.txt

@@ -1,4 +1,3 @@
-numpy>=1.10
+numpy>=1.13
 shapely>=1.5.6
 pyshp>=2
-setuptools>=0.7.2

setup.py

@@ -371,7 +371,6 @@ def decythonize(extensions, **_ignore):
     extras_require=extras_require,
     tests_require=tests_require,
 
-    setup_requires=['setuptools_scm', 'setuptools_scm_git_archive'],
     use_scm_version={
         'write_to': 'lib/cartopy/_version.py',
     },