Remove some now-unused code; etc

.gitignore

@@ -4,6 +4,7 @@
 .pytest_cache/
 .ruffus_history.sqlite
 .venv/
+.venv*/
 *.pyc
 *.sublime-*
 

docs/installation.rst

@@ -118,13 +118,13 @@ install the system version to get most of the dependencies:
         ocrmypdf \
         python3-pip
 
-There are a few dependency changes between ocrmypdf 6.1.2 and 7.x. Let's get
+There are a few system dependency changes since ocrmypdf 6.1.2. Let's get
 these, too.
 
 .. code-block:: bash
 
     sudo apt-get install \
-        libexempi3 \
+        libxml2 \
         pngquant
 
 Then install the most recent ocrmypdf for the local user and set the user's ``PATH`` to check for the user's Python packages.

src/ocrmypdf/helpers.py

@@ -66,10 +66,6 @@ def re_symlink(input_file, soft_link_name, *args, **kwargs):
     os.symlink(os.path.abspath(input_file), soft_link_name)
 
 
-def is_iterable_notstr(thing):
-    return isinstance(thing, Iterable) and not isinstance(thing, str)
-
-
 def page_number(input_file):
     """Get one-based page number implied by filename (000002.pdf -> 2)"""
     return int(os.path.basename(os.fspath(input_file))[0:6])
@@ -125,14 +121,6 @@ def is_file_writable(test_file):
         return True
 
 
-def flatten_groups(groups):
-    for obj in groups:
-        if is_iterable_notstr(obj):
-            yield from obj
-        else:
-            yield obj
-
-
 def deprecated(func):
     """Warn that function is deprecated"""