Avoid importing a non-vendored version of Tornado

Code depending on this conditional import could break if an old version of Tornado is present in the environment, rendering pip unusable. Fixes pypa#10020
bdarnell · May 29, 2021 · 3b655ef · 3b655ef
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commit 3b655ef
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diff --git a/news/10020.bugfix.rst b/news/10020.bugfix.rst
@@ -0,0 +1 @@
+Remove unused optional ``tornado`` import in vendored ``tenacity`` to prevent old versions of Tornado from breaking pip.
diff --git a/src/pip/_vendor/tenacity/__init__.py b/src/pip/_vendor/tenacity/__init__.py
@@ -22,10 +22,9 @@
 except ImportError:
     iscoroutinefunction = None
 
-try:
-    import tornado
-except ImportError:
-    tornado = None
+# Pip does not currently vendor Tornado, so don't import it even if it
+# happens to be installed in the environment.
+tornado = None
 
 import sys
 import threading

diff --git a/tools/vendoring/patches/tenacity.patch b/tools/vendoring/patches/tenacity.patch
@@ -0,0 +1,18 @@
+diff --git a/src/pip/_vendor/tenacity/__init__.py b/src/pip/_vendor/tenacity/__init__.py
+index 5f8cb5058..c2b4d9acc 100644
+--- a/src/pip/_vendor/tenacity/__init__.py
++++ b/src/pip/_vendor/tenacity/__init__.py
+@@ -22,10 +22,9 @@ try:
+ except ImportError:
+     iscoroutinefunction = None
+
+-try:
+-    import tornado
+-except ImportError:
+-    tornado = None
++# Pip does not currently vendor Tornado, so don't import it even if it
++# happens to be installed in the environment.
++tornado = None
+
+ import sys
+ import threading
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Remove unused optional ``tornado`` import in vendored ``tenacity`` to prevent old versions of Tornado from breaking pip.