gh-39457: Remove all__sagemath_categories
    
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It's not used and creates issues with pytest.

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preview.

### ⌛ Dependencies

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URL: #39457
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik

Author: Release Manager

pkgs/sagemath-categories/MANIFEST.in.m4

@@ -42,7 +42,6 @@ global-exclude *.c
 global-exclude *.cpp
 
 global-exclude all__sagemath_*.*
-global-include all__sagemath_categories.py
 
 global-exclude __pycache__
 global-exclude *.py[co]

src/sage/all__sagemath_categories.py

@@ -89,7 +89,6 @@ py.install_sources(
   '__init__.py',
   'all.py',
   'all__sagemath_bliss.py',
-  'all__sagemath_categories.py',
   'all__sagemath_coxeter3.py',
   'all__sagemath_environment.py',
   'all__sagemath_mcqd.py',

src/sage/meson.build

@@ -106,10 +106,7 @@ def unpickle_function(pickled):
 
 
 def call_pickled_function(fpargs):
-    try:
-        import sage.all as toplevel
-    except ImportError:
-        import sage.all__sagemath_categories as toplevel
+    import sage.all as toplevel
     (fp, (args, kwds)) = fpargs
     f = eval("unpickle_function(fp)", toplevel.__dict__, {'fp': fp})
     res = eval("f(*args, **kwds)", toplevel.__dict__,

src/sage/misc/fpickle.pyx

@@ -246,8 +246,7 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
 
     Implicit namespace packages (PEP 420) are only recognized if they
     follow the conventions of the Sage library, i.e., the directory contains
-    a file ``all.py`` or a file matching the pattern ``all__*.py``
-    such as ``all__sagemath_categories.py``.
+    a file ``all.py`` or a file matching the pattern ``all__*.py``.
 
     INPUT: