docs: minor fixes to external Ceph guide

When a path is broken into two separate lines, the generated HTML
includes an incorrect space character in the middle of the path.

We need to ignore doc8 linting on this file as this change breaks the
max line length check. I tried using ``ignore-path-errors`` to exclude
only D001 for this file, but doc8 does not like a relative path for this
option [1].

[1] PyCQA/doc8#162

Change-Id: I1cf0b7a6b7506a68876bce2de5080718280a47be

doc/source/reference/storage/external-ceph-guide.rst

@@ -211,8 +211,7 @@ Cinder for Ceph includes following steps:
 
   * ``/etc/kolla/config/cinder/cinder-volume/ceph.client.cinder.keyring``
   * ``/etc/kolla/config/cinder/cinder-backup/ceph.client.cinder.keyring``
-  * ``/etc/kolla/config/cinder/cinder-backup/
-    ceph.client.cinder-backup.keyring``
+  * ``/etc/kolla/config/cinder/cinder-backup/ceph.client.cinder-backup.keyring``
 
 .. note::
 
@@ -281,8 +280,7 @@ the use with availability zones:
   * ``/etc/kolla/config/cinder/cinder-volume/ceph1.client.cinder.keyring``
   * ``/etc/kolla/config/cinder/cinder-backup/ceph1.client.cinder.keyring``
   * ``/etc/kolla/config/cinder/cinder-backup/ceph2.client.cinder.keyring``
-  * ``/etc/kolla/config/cinder/cinder-backup/
-    ceph2.client.cinder-backup.keyring``
+  * ``/etc/kolla/config/cinder/cinder-backup/ceph2.client.cinder-backup.keyring``
 
 .. note::
 
@@ -296,8 +294,8 @@ Nova must also be configured to allow access to Cinder volumes:
   * ``/etc/kolla/config/nova/ceph.conf``
   * ``/etc/kolla/config/nova/ceph.client.cinder.keyring``
 
-To configure ``different Ceph backend`` for nova-compute host, which
-is useful for the use with availability zones:
+To configure different Ceph backends for nova-compute hosts, which is useful
+for use with availability zones:
 
 * Edit inventory file in the way described below:
 
@@ -364,8 +362,8 @@ Configuring Nova for Ceph includes following steps:
      keys for Cinder and Nova, you will need to override
      ``ceph_nova_user`` to match.
 
-To configure ``different Ceph backend`` for nova-compute host, which
-is useful for the use with availability zones:
+To configure different Ceph backends for nova-compute hosts, which is useful
+for use with availability zones:
 
 Edit inventory file in the way described below:
 

tox.ini

@@ -126,6 +126,11 @@ show-source = True
 ignore = W504
 exclude = .eggs,.git,.tox,doc
 
+[doc8]
+# NOTE(priteau): We break max line length in this file to avoid inserting
+# erroneous space characters inside file paths
+ignore-path = doc/source/reference/storage/external-ceph-guide.rst
+
 [testenv:doc8]
 deps = {[testenv:linters]deps}
 commands =