fix: update pip version constraint to avoid compatibility issues with pip-tools (#194)

This adds a version constraint to prevent pip from upgrading to version 25.x, which is incompatible with the currently-used pip-tools 7.5.1.

The constraint addresses an AttributeError related to 'use_pep517' that occurs when pip 25.x is used with pip-tools 7.5.1.

Author: ttak-apphelix

requirements/constraints.txt

@@ -10,3 +10,9 @@
 
 # Common constraints for edx repos
 -c https://raw.githubusercontent.com/edx/edx-lint/master/edx_lint/files/common_constraints.txt
+
+# pip 25.3 is incompatible with pip-tools hence causing failures during the build process 
+# Make upgrade command and all requirements upgrade jobs are broken due to this.
+# See issue https://github.com/edx/devstack/issues/195 for details regarding the ongoing fix.
+# The constraint can be removed once a release (pip-tools > 7.5.1) is available with support for pip 25.3
+pip<25.3