_Py_InitializeCore: main interpreter already initialized

[imyxh]

I get these odd error messages when trying to build:

==> Starting build()...
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored Scripts/fontbuilder.py
--- Scripts/fontbuilder.py      (original)
+++ Scripts/fontbuilder.py      (refactored)
@@ -69,9 +69,9 @@
     bitmap_max = 1 << count

     # Iterate over all possible permutations
-    for i in xrange(bitmap_max):
+    for i in range(bitmap_max):
         # Map the iteration's permutations using a bitmap
-        bitmap = [i >> n & 1 for n in xrange(count)]
+        bitmap = [i >> n & 1 for n in range(count)]
         for opts in _expand_options(bitmap):
             yield(int(float(i)/bitmap_max*100), opts)

@@ -96,7 +96,7 @@
         variant = '-'.join(variants) or 'Normal'
         variant_dir = join(dstdir, variant)

-        print('Generating ' + variant_dir)
+        print(('Generating ' + variant_dir)) 
     mkdir_p(join(variant_dir, 'TTF'))
     mkdir_p(join(variant_dir, 'OTF'))
RefactoringTool: Files that were modified:
RefactoringTool: Scripts/fontbuilder.py
mkdir -p Variants
Scripts/validate-font "Sources/FantasqueSansMono-Bold.sfdir"
Validating FantasqueSansMono-Bold... 
Fatal Python error: _Py_InitializeCore: main interpreter already initialized

Current thread 0x00007fedbff6d940 (most recent call first):
Error in FantasqueSansMono-Bold.
make: *** [Makefile:15: Variants/Normal/TTF/FantasqueSansMono-Bold.ttf] Error 134

I don't really know how to make heads or tails of this Python error, but I'm installing from Arch Linux where /usr/bin/python symlinks to python3. Could that be it?