coding style: Extract the paging code into its own context manager

eris/__main__.py

@@ -1109,20 +1109,26 @@ def manage_cache(root_path):
             gitignore_file.write("*")
 
 
+@contextlib.contextmanager
+def print_to_pager(pager_command=["less", "-RFEX"]):
+    try:
+        pager_process = subprocess.Popen(pager_command, stdin=subprocess.PIPE, text=True)
+    except FileNotFoundError:
+        yield
+    else:
+        with contextlib.redirect_stdout(pager_process.stdin):
+            yield
+        pager_process.stdin.close()
+        pager_process.wait()
+
+
 def print_tool_info():
     extensions_for_tool = {}
     for extensions, tools_ in tools.TOOLS_FOR_EXTENSIONS:
         for extension in extensions:
             for tool in tools_:
                 extensions_for_tool.setdefault(tool, {extension}).add(extension)
-    pager_process = None
+    with print_to_pager():
-    if shutil.which("less"):
-        pager_process = subprocess.Popen(["less", "-RFEX"],
-                                         stdin=subprocess.PIPE, text=True)
-        output_file = pager_process.stdin
-    else:
-        output_file = sys.stdout
-    with contextlib.redirect_stdout(output_file):
         for tool in sorted(tools.tools_all(), key=lambda t: t.__name__):
             print(termstr.TermStr(tool.__name__, is_bold=True) if tools.is_tool_available(tool)
                   else termstr.TermStr(tool.__name__, fg_color=termstr.Color.red) + " (not available)")
@@ -1134,9 +1140,6 @@ def print_tool_info():
             extensions = list(extensions_for_tool.get(tool, {"*"}))
             print("extensions:", ", ".join(extensions))
             print("")
-    if pager_process is not None:
-        output_file.close()
-        pager_process.wait()
 
 
 def install_all_tools():