Test against pip==23.2.1 (#190)

Fixes #189.

Author: di

tox.ini

@@ -1,10 +1,10 @@
 [tox]
 envlist=
-    py37-pip{232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203,2024,2023,2022,2021,202,201,2002,2001,1931,193,1923,1922,1921,192,1911,191,1903,1902,1901,190,181},
-    py38-pip{232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203,2024,2023,2022,2021,202,201,2002,2001,1931},
-    py39-pip{232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203},
-    py310-pip{232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213},
-    py311-pip{232,2312,2311,231,2301,230,2231,223,2222,2221,222},
+    py37-pip{2321,232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203,2024,2023,2022,2021,202,201,2002,2001,1931,193,1923,1922,1921,192,1911,191,1903,1902,1901,190,181},
+    py38-pip{2321,232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203,2024,2023,2022,2021,202,201,2002,2001,1931},
+    py39-pip{2321,232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213,2124,2123,2122,2121,212,2113,2112,2111,211,2101,210,2034,2033,2031,203},
+    py310-pip{2321,232,2312,2311,231,2301,230,2231,223,2222,2221,222,2212,2211,221,2204,2203,2202,2201,220,2131,213},
+    py311-pip{2321,232,2312,2311,231,2301,230,2231,223,2222,2221,222},
     lint
 
 [testenv]
@@ -13,6 +13,7 @@ deps=
     pretend
     pytest
     virtualenv>20
+    pip2321: pip==23.2.1
     pip232: pip==23.2
     pip2312: pip==23.1.2
     pip2311: pip==23.1.1