[stable-only] Add font for PDF generation and fix lower constraints

openstack-tox-docs job started to fail with the following error:

! LaTeX Error: File `tgtermes.sty' not found.

This patch adds the required font package to bindep doc profile.

With the new pip resolver (introduced in pip 20.3) the constraints
checking is now working better, thus reveals multiple constrain
conflicts. This patch also fixes those problems:
- no extra is allowed for constraints
- futurist 1.8.0 depends on six>=1.10.0
- keystoneauth1 3.9.0 depends on requests>=2.14.2
- oslo.upgradecheck==0.1.1 was not listed among lower constraints

Conflicts:
    lower-constraints.txt
    requirements.txt

Change-Id: I00c994316653446748823867eb7c1a1ba5abfbea
(cherry picked from commit 418af55c7b)

bindep.txt

@@ -5,3 +5,6 @@ build-essential [platform:dpkg]
 libffi-dev [platform:dpkg]
 gettext [platform:dpkg]
 python37 [platform:rpm py37]
+
+# PDF Docs package dependencies
+tex-gyre [platform:dpkg doc]

lower-constraints.txt

@@ -20,10 +20,10 @@ oslo.config==5.2.0
 oslo.i18n==3.15.3
 oslo.log==3.36.0
 oslo.messaging==6.2.0
-oslo.messaging[kafka]==6.2.0
 oslo.privsep==1.32.0
 oslo.reports==1.18.0
 oslo.rootwrap==2.0.0
+oslo.upgradecheck==0.1.1
 oslo.utils==3.37.0
 oslo.vmware==2.17.0
 oslotest==3.2.0
@@ -39,12 +39,12 @@ python-novaclient==9.1.0
 python-swiftclient==3.2.0
 python-zaqarclient==1.3.0
 PyYAML==3.12
-requests==2.8.1
+requests==2.14.2
 requests-aws==0.1.4
-six==1.9.0
+six==1.10.0
 stestr==2.0.0
 stevedore==1.20.0
 tenacity==4.4.0
 testscenarios==0.4
 testtools==2.2.0
-tooz[zake]==1.47.0
+tooz==1.47.0

requirements.txt

@@ -28,8 +28,8 @@ python-novaclient>=9.1.0 # Apache-2.0
 python-swiftclient>=3.2.0 # Apache-2.0
 python-cinderclient>=3.3.0  # Apache-2.0
 PyYAML>=3.12 # MIT
-requests!=2.9.0,>=2.8.1 # Apache-2.0
-six>=1.9.0 # MIT
+requests>=2.14.2 # Apache-2.0
+six>=1.10.0 # MIT
 stevedore>=1.20.0 # Apache-2.0
 tenacity>=4.4.0  # Apache-2.0
 tooz[zake]>=1.47.0 # Apache-2.0