Make Python 3.8 minimum requirement

docs/api.rst

@@ -72,14 +72,6 @@ OCRmyPDF, use processes.
     not take at least one of these steps, process semantics will prevent
     OCRmyPDF from working correctly.
 
-.. warning::
-
-    On macOS with Python 3.7, you must call
-    :func:`multiprocessing.set_start_method("spawn")`. Without this, multiprocessing
-    will be unstable. From the command line, OCRmyPDF does this automatically,
-    but as an API user you must do this. See Python bpo-33725 for details.
-    Python 3.8+ also resolve this automatically.
-
 Logging
 -------
 

docs/installation.rst

@@ -417,7 +417,7 @@ Native Windows
 
 You must install the following for Windows:
 
-* Python 3.7 (64-bit) or later
+* Python 3.8 (64-bit) or later
 * Tesseract 4.0 or later
 * Ghostscript 9.50 or later
 
@@ -649,7 +649,7 @@ unfortunately, the ``pip install`` command cannot satisfy all of them.
 Installing HEAD revision from sources
 =====================================
 
-If you have ``git`` and Python 3.7 or newer installed, you can install
+If you have ``git`` and Python 3.8 or newer installed, you can install
 from source. When the ``pip`` installer runs, it will alert you if
 dependencies are missing.