Fix docs changelog build logic

docs/conf.py

@@ -36,10 +36,21 @@
 """
 )
 
-with open(new_changelog) as fr:
-    if fr.read() != CHANGELOG_TEXT:  # Only write if it's changed to avoid recompiling
-        with open(new_changelog, "w") as fw:
-            fw.write(CHANGELOG_TEXT)
+# Only write if it's changed to avoid recompiling the docs
+def write_new():
+    with open(new_changelog, "w") as fw:
+        fw.write(CHANGELOG_TEXT)
+
+
+try:
+    c_file = open(new_changelog)
+except FileNotFoundError:
+    write_new()
+else:
+    if c_file.read() != CHANGELOG_TEXT:
+        write_new()
+    c_file.close()
+
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the