Move Babel and argparse from test-requirements.txt

to requirements.txt, to avoid disk-image-create failed without
dependencies installed.

Change-Id: I110809d298593890b2b050d6da2dcbd036db1ff3

requirements.txt

@@ -0,0 +1,2 @@
+Babel>=1.3
+argparse

test-requirements.txt

@@ -4,5 +4,3 @@ coverage>=3.6
 discover
 testrepository>=0.0.17
 testtools>=0.9.32
-Babel>=1.3
-argparse

tox.ini

@@ -9,7 +9,8 @@ install_command = pip install -U {opts} {packages}
 setenv = LANG=en_US.UTF-8
          LANGUAGE=en_US:en
          LC_ALL=C
-deps= -r{toxinidir}/test-requirements.txt
+deps= -r{toxinidir}/requirements.txt
+      -r{toxinidir}/test-requirements.txt
 commands=
     python setup.py testr --slowest --testr-args='{posargs}'