Pin some dependency versions now that some of the limits are known

README.md

@@ -99,6 +99,12 @@ python3 -m pip install lxml
 python3 -m pip install pyenchant
 ```
 
+PyQt/Qt should be at least 5.2.1, but ideally 5.10 or higher for nearly all features to work.
+Exporting to markdown requires PyQt/Qt 5.14.
+There are no known minimum for lxml, but the code was originally written with 4.2.
+The optional spell check library must be at least 3.0.0 to work with Windows.
+On Linux, 2.0.0 also works fine.
+
 If no external spell checking tool is installed, novelWriter will use a basic spell checker based on standard Python package `difflib`.
 Currently, only English dictionaries are available for this spell checker, but more can be added to the `nw/assets/dict` folder.
 See the [nw/assets/dict/README.md](README.md) file in that folder for how to generate more dictionaries.

docs/source/started.txt

@@ -35,6 +35,11 @@ The following are optional, but recommended:
 
 * ``pyenchant`` for spell checking
 
+PyQt/Qt should be at least 5.2.1, but ideally 5.10 or higher for nearly all features to work.
+Exporting to markdown requires PyQt/Qt 5.14.
+There are no known minimum for lxml, but the code was originally written with 4.2.
+The optional spell check library must be at least 3.0.0 to work with Windows.
+On Linux, 2.0.0 also works fine.
 
 Running novelWriter
 ===================

requirements.txt

@@ -1,3 +1,3 @@
-pyqt5
+pyqt5>=5.2.1
-lxml
+lxml>=4.2.0
-pyenchant
+pyenchant>=3.0.0

setup.py

@@ -37,8 +37,8 @@ setuptools.setup(
     ],
     python_requires = ">=3.6",
     install_requires = [
-        "pyqt5",
+        "pyqt5>=5.2.1",
-        "lxml",
+        "lxml>=4.2.0",
-        "pyenchant",
+        "pyenchant>=3.0.0",
     ],
 )