Fix tox syntax error

Author: wenbinf

tox.ini

@@ -7,7 +7,7 @@
 envlist =
     fmt
     lint
-    py{310,39,38,37,36,35,py3}
+    py{310,39,38,37}
 skip_missing_interpreters = true
 
 [tool:pytest]
@@ -21,12 +21,12 @@ setenv =
     COVERAGE_FILE = {toxworkdir}/.coverage.{envname}
 deps =
     coverage >= 5
-    py{310,39,38,37,36,35,py3}: pytest >= 6.0.0
+    py{310,39,38,37}: pytest >= 6.0.0
     pytest-cov >= 2.8.1, < 2.11.0
     pytest-mock >= 2.0.0
     pytest-xdist >= 1.31.0
 commands = pytest --cov {posargs:-n auto}
-passenv = LDFLAGS CFLAGS
+passenv = LDFLAGS,CFLAGS
 
 [testenv:fmt]
 description = run code formatting using black