diff --git a/src/sage/doctest/__main__.py b/src/sage/doctest/__main__.py
index 42a80f78a1a..5b2014bfc92 100644
--- a/src/sage/doctest/__main__.py
+++ b/src/sage/doctest/__main__.py
@@ -3,6 +3,8 @@
 import sys
 import shlex
 
+import pytest
+
 # Note: the DOT_SAGE and SAGE_STARTUP_FILE environment variables have already been set by sage-env
 DOT_SAGE = os.environ.get('DOT_SAGE', os.path.join(os.environ.get('HOME'),
                                                    '.sage'))
@@ -159,6 +161,9 @@ def __call__(self, parser, namespace, values, option_string=None):
 
 
 def main():
+    from sage.doctest.control import DocTestController
+    from sage.env import SAGE_SRC
+
     parser = _make_parser()
     # custom treatment to separate properly
     # one or several file names at the end
@@ -191,44 +196,30 @@ def main():
 
     os.environ["SAGE_NUM_THREADS"] = "2"
 
-    from sage.doctest.control import DocTestController
     DC = DocTestController(args, args.filenames)
     err = DC.run()
 
-    # Issue #33521: Do not run pytest if the pytest configuration is not available.
-    # This happens when the source tree is not available and SAGE_SRC falls back
-    # to SAGE_LIB.
-    from sage.env import SAGE_SRC
-    if not all(os.path.isfile(os.path.join(SAGE_SRC, f))
-               for f in ["conftest.py", "tox.ini"]):
-        return err
-
-    try:
-        exit_code_pytest = 0
-        import pytest
-        pytest_options = []
-        if args.verbose:
-            pytest_options.append("-v")
-
-        # #35999: no filename in arguments defaults to "src"
-        if not args.filenames:
-            filenames = [SAGE_SRC]
-        else:
-            # #31924: Do not run pytest on individual Python files unless
-            # they match the pytest file pattern.  However, pass names
-            # of directories. We use 'not os.path.isfile(f)' for this so that
-            # we do not silently hide typos.
-            filenames = [f for f in args.filenames
-                         if f.endswith("_test.py") or not os.path.isfile(f)]
-        if filenames:
-            print(f"Running pytest on {filenames} with options {pytest_options}")
-            exit_code_pytest = pytest.main(filenames + pytest_options)
-            if exit_code_pytest == 5:
-                # Exit code 5 means there were no test files, pass in this case
-                exit_code_pytest = 0
-
-    except ModuleNotFoundError:
-        print("pytest is not installed in the venv, skip checking tests that rely on it")
+    exit_code_pytest = 0
+    pytest_options = []
+    if args.verbose:
+        pytest_options.append("-v")
+
+    # #35999: no filename in arguments defaults to "src"
+    if not args.filenames:
+        filenames = [SAGE_SRC]
+    else:
+        # #31924: Do not run pytest on individual Python files unless
+        # they match the pytest file pattern.  However, pass names
+        # of directories. We use 'not os.path.isfile(f)' for this so that
+        # we do not silently hide typos.
+        filenames = [f for f in args.filenames
+                        if f.endswith("_test.py") or not os.path.isfile(f)]
+    if filenames:
+        print(f"Running pytest on {filenames} with options {pytest_options}")
+        exit_code_pytest = pytest.main(filenames + pytest_options)
+        if exit_code_pytest == 5:
+            # Exit code 5 means there were no test files, pass in this case
+            exit_code_pytest = 0
 
     if err == 0:
         return exit_code_pytest
diff --git a/src/sage/misc/dev_tools.py b/src/sage/misc/dev_tools.py
index 90f41f8b0f4..31bc87bdb93 100644
--- a/src/sage/misc/dev_tools.py
+++ b/src/sage/misc/dev_tools.py
@@ -64,10 +64,11 @@ def runsnake(command):
         - :class:`Profiler`
     """
     import cProfile
-    from sage.misc.temporary_file import tmp_filename
+
     from sage.misc.misc import get_main_globals
-    from sage.repl.preparse import preparse
     from sage.misc.superseded import deprecation
+    from sage.misc.temporary_file import tmp_filename
+    from sage.repl.preparse import preparse
 
     deprecation(39274, "just use the runsnake program directly")
 
@@ -176,9 +177,10 @@ def load_submodules(module=None, exclude_pattern=None):
         load sage.geometry.polyhedron.palp_database... succeeded
         load sage.geometry.polyhedron.ppl_lattice_polygon... succeeded
     """
-    from .package_dir import walk_packages
     import importlib
 
+    from .package_dir import walk_packages
+
     if module is None:
         import sage
         module = sage
@@ -276,7 +278,7 @@ def find_objects_from_name(name, module_name=None, include_lazy_imports=False):
     from sage.misc.lazy_import import LazyImport
 
     obj = []
-    for smodule_name, smodule in sys.modules.items():
+    for smodule_name, smodule in list(sys.modules.items()):
         if module_name and not smodule_name.startswith(module_name):
             continue
         if hasattr(smodule, '__dict__') and name in smodule.__dict__:
@@ -462,8 +464,9 @@ def import_statements(*objects, **kwds):
         detect deprecated stuff). So, if you use it, double check the answer and
         report weird behaviors.
     """
-    import itertools
     import inspect
+    import itertools
+
     from sage.misc.lazy_import import LazyImport
 
     answer = defaultdict(list)