Add snappy, swap channels, pin 3.6

Author: brl0

.github/workflows/test.yml

@@ -28,7 +28,7 @@ jobs:
         shell: bash -l {0}
     env:
       PYTHON_VERSION: ${{ matrix.python-version }}
-      CHANS_DEV: "-c pyviz/label/dev -c conda-forge"
+      CHANS_DEV: "-c conda-forge -c pyviz/label/dev"
       CHANS_OSX: "-c pyviz/label/dev -c conda-forge"
       CHANS: "-c pyviz"
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

setup.py

@@ -30,6 +30,7 @@
     'pandas>=0.25',
     'param',
     'retrying',
+    'snappy',
 ]
 
 if sys.platform == 'darwin':
@@ -38,10 +39,16 @@
         'pyarrow>=0.15,<2',
     ])
 else:
-    install_requires.extend([
-        'numpy>=1.20',
-        'pyarrow>=3',
-    ])
+    if sys.version_info[:2] == (3, 6):
+        install_requires.extend([
+            'numpy<1.20',
+            'pyarrow<3',
+        ])
+    else:
+        install_requires.extend([
+            'numpy>=1.20',
+            'pyarrow<3',
+        ])
 
 setup_args = dict(
     name='spatialpandas',