warn against sorting requirements

Change-Id: I64ae9191863564e278a35d42ec9cd743a233028e
Addresses-Bug: #1365061

requirements-py3.txt

@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 alembic>=0.6.4
 anyjson>=0.3.3
 argparse

requirements.txt

@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 alembic>=0.6.4
 anyjson>=0.3.3
 argparse

test-requirements-py3.txt

@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 # Hacking already pins down pep8, pyflakes and flake8
 hacking>=0.9.2,<0.10
 Babel>=1.3

test-requirements.txt

@@ -1,3 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 # Hacking already pins down pep8, pyflakes and flake8
 hacking>=0.9.2,<0.10
 Babel>=1.3