script to fix lower constraints entries that do not match local requirements

We have a few projects that have lower constraints lists that do not
match their own local requirements settings. This script tries to fix
that by changing the constraints to match.

Change-Id: I5f9bfc30e5dab855c9cef77cd9c4063658aab4c1
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

tools/fix-lower-constraints.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+"""
+Instructions:
+
+ 1. virtualenv venv
+ 2. source virtualenv/bin/activate
+ 3. pip install /path/to/local/copy/of/requirements/repository
+ 4. cd /path/to/project/to/fix
+ 5. .../requirements/tools/fix-lower-constraints.py > new-lc.txt
+ 6. mv new-lc.txt lower-constraints.txt
+ 7. Update the patch and resubmit it to gerrit.
+"""
+
+import io
+
+from openstack_requirements import requirement
+
+
+def read_file(name):
+    with io.open(name, 'r', encoding='utf-8') as f:
+        return requirement.parse(f.read())
+
+
+requirements = read_file('requirements.txt')
+requirements.update(read_file('test-requirements.txt'))
+constraints = read_file('lower-constraints.txt')
+
+output = []
+
+for const in constraints.values():
+    const = const[0][0]
+    actual = const.specifiers.lstrip('=')
+    name = const.package.lower()
+    if name not in requirements:
+        # Ignore secondary dependencies
+        output.append(const.to_line())
+        continue
+    for req, _ in requirements[name]:
+        min = [
+            s
+            for s in req.specifiers.split(',')
+            if '>' in s
+        ]
+        if not min:
+            # If there is no lower bound, assume the constraint is
+            # right.
+            output.append(const.to_line())
+            continue
+        required = min[0].lstrip('>=')
+        if required != actual:
+            output.append('{}=={}\n'.format(
+                const.package, required))
+        else:
+            output.append(const.to_line())
+
+for line in sorted(output, key=lambda x: x.lower()):
+    if not line.strip():
+        continue
+    print(line.rstrip())