Fix tabs in Makefile

Author: stefanv

Makefile

@@ -6,8 +6,8 @@ LESSONS_DIR = lessons
 GENERATED_LESSONS_DIR = book/lessons
 
 _requirements.installed:
-    pip install -q -r requirements.txt
-    touch _requirements.installed
+	pip install -q -r requirements.txt
+	touch _requirements.installed
 
 MARKDOWNS = $(wildcard $(LESSONS_DIR)/*.md)
 MD_OUTPUTS = $(patsubst $(LESSONS_DIR)/%.md, $(GENERATED_LESSONS_DIR)/%.md, $(MARKDOWNS))
@@ -16,25 +16,25 @@ NOTEBOOKS = $(patsubst %.md, %.ipynb, $(MD_OUTPUTS))
 .SECONDARY: $(MD_OUTPUTS) $(NOTEBOOKS)
 
 $(GENERATED_LESSONS_DIR)/%.ipynb:$(LESSONS_DIR)/%.md book/lessons book/lessons/images
-        # This does not work, due to bug in notedown; see https://github.com/aaren/notedown/issues/53
-    #notedown --match=python --precode='%matplotlib inline' $< > $@
-    notedown --match=python $< > $@
-    jupyter nbconvert --execute --inplace $@ --ExecutePreprocessor.timeout=-1
+	# This does not work, due to bug in notedown; see https://github.com/aaren/notedown/issues/53
+	#notedown --match=python --precode='%matplotlib inline' $< > $@
+	notedown --match=python $< > $@
+	jupyter nbconvert --execute --inplace $@ --ExecutePreprocessor.timeout=-1
 
 %.md:%.ipynb
-    jupyter nbconvert --to=mdoutput --output="$(notdir $@)" --output-dir=$(GENERATED_LESSONS_DIR) $<
+	jupyter nbconvert --to=mdoutput --output="$(notdir $@)" --output-dir=$(GENERATED_LESSONS_DIR) $<
 #	$(eval NBSTRING := [📂 Download lesson notebook](.\/$(basename $(notdir $@)).ipynb)\n\n)
 #	sed -i'.bak' '1s/^/$(NBSTRING)/' $@
 
 book/lessons:
-    mkdir -p book/lessons
+	mkdir -p book/lessons
 
 book/lessons/images:
-    ln -s ${PWD}/lessons/images ${PWD}/book/lessons/images
+	ln -s ${PWD}/lessons/images ${PWD}/book/lessons/images
 
 html: | _requirements.installed $(NOTEBOOKS) $(MD_OUTPUTS)
-    @export SPHINXOPTS=-W; make -C book html
-    cp $(GENERATED_LESSONS_DIR)/*.ipynb book/build/html/lessons/
+	@export SPHINXOPTS=-W; make -C book html
+	cp $(GENERATED_LESSONS_DIR)/*.ipynb book/build/html/lessons/
 
 clean:
-    rm -rf $(GENERATED_LESSONS_DIR)/*
+	rm -rf $(GENERATED_LESSONS_DIR)/*