"pip install -e foo -r reqs.txt" fails if 'foo' is in reqs.txt;

gistfile1.txt

mg@platonas! ~ $ cd /tmp

mg@platonas! /tmp $ mkdir foo

mg@platonas! /tmp $ vim foo/setup.py

[10s]
mg@platonas! /tmp $ virtualenv venv
Using real prefix '/usr'
New python executable in venv/bin/python
Installing setuptools, pip, wheel...done.

mg@platonas! /tmp $ echo foo > r.txt

mg@platonas! /tmp $ venv/bin/pip install -e foo -r r.txt
Obtaining file:///tmp/foo
Collecting foo (from -r r.txt (line 1))
  Could not find a version that satisfies the requirement foo (from -r r.txt (line 1)) (from versions: )
No matching distribution found for foo (from -r r.txt (line 1))

[exited with 1]
mg@platonas! /tmp $ venv/bin/pip install -e foo
Obtaining file:///tmp/foo
Installing collected packages: foo
  Running setup.py develop for foo
Successfully installed foo

mg@platonas! /tmp $ venv/bin/pip install -r r.txt
Requirement already satisfied (use --upgrade to upgrade): foo in ./foo (from -r r.txt (line 1))

mg@platonas! /tmp $