make pants tailor ignore python_requirements targets

these requirements files will eventually be deleted.
Including duplicate requirements definitions makes dependency inferrence
ambiguous in pants, so we need to avoid adding duplicates.

pants.toml

@@ -14,6 +14,19 @@ pants_ignore.add = [
   # TODO: remove these once we start building wheels with pants.
   "dist_utils.py",
   "setup.py",
+  # keep tailor from using legacy requirements files (not for pants)
+  "contrib/examples/requirements.txt",
+  "contrib/hello_st2/requirements.txt",
+  "contrib/runners/*/in-requirements.txt",
+  "contrib/runners/*/requirements.txt",
+  "st2*/in-requirements.txt",
+  "st2*/requirements.txt",
+  "st2common/tests/fixtures/requirements-used-for-tests.txt",
+  "/fixed-requirements.txt",
+  "/test-requirements.txt",
+  # keep requirements.txt for now. We might ignore it if we need an alternate interrim
+  # file that is decoupled from our legacy requirements files generation.
+  # "/requirements.txt",
 ]
 
 [source]